In October 2007, Katherine Olson was looking for work. Since graduating summa cum laude from St. Olaf College in Northfield, Minn., with a dual degree in theater and Hispanic studies, she'd mostly cobbled together part-time jobs—waitressing, teaching Spanish, coaching high-school speech.Olson was looking at nanny listings on Craigslist when she came across an ad from a mother who needed someone to look after her 5-year-old daughter. Olson sent an e-mail saying she was interested, and the mother, Amy, agreed to hire her for 10:30 a.m. to 5 p.m. on Thursday the 25th. Amy sent along her address in nearby Savage, about 18 miles southwest of Minneapolis.A pretty 24-year-old with freckles and tight red curls, Olson wore a pink fleece jacket and spandex stretch pants on the day of the babysitting job. She parked her gold 2003 Hyundai Elantra outside the light teal home and walked up the paved driveway.But when the front door opened, it wasn't Amy who answered. It was a paunchy young man with acne, armed with a Ruger .357 Magnum Blackhawk revolver.His name was Michael Anderson, and he would soon be dubbed "The Craigslist Killer."When Craig Newmark began sending out e-mails to his buddies during the winter of 1995, he had no intention of starting a multimillion-dollar business. A recent transplant to San Francisco whose countercultural streak belied a disarming shyness, Newmark simply wanted to keep fellow computer geeks abreast of events throughout the Bay Area.Word spread quickly. During the ensuing months, droves of new members subscribed and began posting their own ads. Newmark made no attempt to moderate and let the list grow organically. Within a year, Craigslist had come to resemble more a digital classifieds section than a mere e-mail list. When Newmark began organizing posts by categories, the transition was complete. In 1999 he incorporated the site, making it a for-profit outfit, but nonetheless stuck with the dot-org domain name to reflect its self-described "noncommercial nature."The site experienced exponential growth during the mid-2000s thanks to its intuitive, no-frills layout and great word-of-mouth. Although Newmark refuses to disclose his financials, estimates by industry observers with the AIM Group suggest that between 2003 and 2008 Craigslist's revenues skyrocketed from $7 million to $81 million."We arrived at those figures the simplest way imaginable," says Peter Zollman, AIM Group's founder. "We counted ads."Users post more than 40 million new ads per month, according to the site's fact sheet, making it by far the world's largest source of classified advertising in any medium. The site that once catered exclusively to Newmark's Bay Area pals has established itself in 570 cities in 50 countries and produces upward of 22 billion page views per month.Newmark attributes his site's success to its DIY format. Unencumbered by registration fees or account requirements, commerce flourishes.But it's precisely this anything-goes ethic that has politicians and law enforcement officials around the country gunning for w's brainchild. They point to the popular Erotic Services category—intended for legal trades such as phone sex and escorts—as a cesspool of prostitution."Prostitution is not a victimless crime," says Connecticut Attorney General Richard Blumenthal, who has spearheaded a national campaign to pressure the site to clean up its act: "Prostitution ads, pornography, and other promotions of illicit activity can lead to the kind of horrific tragedies we've been seeing."He's referring of course to the recent spate of headline-grabbing murders that have made "Craigslist Killer" a top Google search term. In February, a Dallas man was found guilty of capital murder for killing a 21-year-old man who responded to his Craigslist ad for a 1995 Chevrolet Caprice. In March, New York City police discovered the body of WABC radio newsman George Weber—he'd been stabbed to death by a 16-year-old knife fetishist he'd solicited via Craigslist. Three weeks later, Boston University medical student Philip Markoff was arrested and accused of murdering a prostitute he'd solicited through Craigslist. And last month, authorities nabbed a man in Kent after he allegedly posted a Craigslist ad, titled "A strange desire," with the intent to solicit a woman to have sex with and then kill."My phone's been off the hook," says Trench Reynolds, a Charlotte, N.C., blogger who's been tracking what he calls "Craigslist crimes" since August 2007. "It's been surreal. I was on CNN last night. The Boston Globe, The [Quincy, Mass.] Patriot Ledger, I'm talking with CBS right now."In an attempt to tamp down the hysteria, both Newmark and Craigslist CEO Jim Buckmaster have taken to the TV airwaves. Both men were greeted with considerable skepticism. Newmark's April 24 appearance on Nightline came across less as an interview than as an ambush, with the balding computer programmer cornered at his desk by interviewer Martin Bashir. Buckmaster's interview on CNN that same week was more cordial and nuanced, but he was nonetheless on the defensive.In full damage-control mode, Newmark has become considerably harder to reach, rebuffing The New York Times and The Boston Globe and insisting on seeing interview questions ahead of time.Which makes it all the more remarkable that this past Sunday, May 3, he spoke in public, at a memorial concert in Katherine Olson's honor.Before a throng of cameras, the Olson family stood shoulder-to-shoulder in front of their home in Cottage Grove, Minn., to address the world. Katherine's father, Rolf, and her brother, Karl, bookended her mother Nancy and sister Sarah Richter. It was the day after they had received news of Katherine's death. Their heads looked heavy as they took questions from the press."We know where Katherine is," said Nancy. "So we are not afraid for Katherine. We will miss her terribly. She was a bright light and free spirit."Early the following week, Rolf went into his office at Richfield Lutheran Church, where he serves as a pastor. Among the mail was a FedEx envelope from San Francisco. He looked at the name, but couldn't make it out. He opened it up and found a letter from Craig Newmark. It took him a moment to realize it was the "Craig" from Craigslist."Nothing fancy, just a sheet of paper with his handwritten message with his sincere condolence," Rolf says. "And he said, 'Please contact me if you want to talk further. Here's my e-mail, here's my phone number, I'm available anytime.'"That Wednesday, October 31, 2007, Rolf took a seat with his family in the first pew of Christ Presbyterian Church in the Minneapolis suburb of Edina. Surrounding them were 1,600 friends, family members, and classmates of Katherine, along with the police officers who investigated the case."We may never know why there had to be such a violent and senseless death," Reverend Tom Koelln told the mourners. "But we know that the darkness will not overcome the light."A few days later, Rolf found himself once again at his church office. He remembered the letter from Newmark and decided to contact him. "I did e-mail him and said, 'Thank you for your condolence,'" Rolf recalls. "And while I was still sitting in the office I got an e-mail back from him. I mean, it was like ping-ping. Again he said, 'If there is anything we can do to support your efforts, don't hesitate to contact me.'"Throughout the ordeal, the family members took walks around their neighborhood to think. It was during these talks that they came up with the idea for a memorial concert in Katherine's honor. "We thought, 'Wouldn't it be a cool idea?,'" recalls Nancy.Rolf thought back to his contact with Newmark, but he wasn't sure how to approach the company. He spent hours crafting a concise message. "So I sent an e-mail off to Jim Buckmaster, their CEO, and was hoping I was very clear with purposes for the concert and what my costs were and asked would they care to donate," says Rolf.Buckmaster wrote back a message in all lower-case letters: "sure. sounds great... let us know what you need.""It was so informal," remembers Sarah, Katherine's older sister. "And that's how they are. It's like a brief text you would send to your friend."A year and a half later, inside the Scott County courtroom, the parents of Katherine Olson sat across the aisle from the parents of Michael Anderson as though they were in a wedding they never wanted. Surrounding them were more Olson family members, friends, parishioners from Rolf's church, and law enforcement personnel involved with the case. The 40-seat gallery was filled to capacity.Michael Anderson entered the courtroom in a blue suit and kept to himself as his attorney, Alan Margoles, detailed his sex life."Remember," said Margoles. "Michael Anderson was a dumb kid. He had no girlfriend, never dated, never went to a high-school dance, and never held a girl's hand."Margoles wanted to show that his client lured Katherine to the home in Savage for sex, and not, as prosecutors put forth, with the intent to kill.The opening day saw Nancy Olson take the stand to tell the jury about the final time she saw her daughter. It was when Katherine was singing in church choir.Prosecutors asked when she saw her daughter next."The next time I saw her she was in a casket at Morris Nilsen Funeral Home," Nancy said. "And she was cold and smelled like chemicals."The next day, Barbara Anderson took the stand to talk about her son. The soft-spoken mother wore her hair parted in the center, and politely detailed how, on the day of the murder, Michael had come home from work just like any other day. "That's just Michael," Barbara would say later. "He never really talked unless he had a fun time off-roading in his truck."Prior to the hearing, Craigslist had helped law enforcement by assembling a 127-page dossier on Michael Anderson's use of the Web site. The company also dispatched Clint Powell to take the stand. The customer-service manager was familiar with the technical workings of Craigslist.Powell told the courtroom how Anderson first used Craigslist as a way to find ice-fishing gear, truck parts, and collectible plates with misspelled words like "Star Terk." This pattern changed in October 2007 as Anderson started trolling for women. Powell read various postings made by Anderson. One said, "looks and size don't mean a lot to me. I'm not little man, but I'm not huge either." Another read, "Looking for fresh faces for a new video and Web site...new talent only. Also need 18 plus virgin willing to be in a video."The entire time Anderson sat motionless, staring straight ahead."I don't think he made eye contact with a single person the entire trial," says Margoles. "He was the quietest defendant I've ever had."On day five of the trial, Anderson's former cellmate, Gregory Wikan, took the stand. He told the jury how Anderson had boasted about being known as the "Craigs-list Killer."Again, Anderson stared straight ahead, refusing to make eye contact.The final day of testimony saw Detective Laura Kvasnicka take the stand as the last witness. She detailed the life Anderson led online, including multiple attempts to lure women to his home. He looked for no-strings-attached hookups, posting one such advertisement just hours before killing Katherine.It took five hours for the jury to return its verdict. The Olson family held one another as the 12-member jury announced the news: Michael Anderson was guilty of first- and second-degree murder, as well as second-degree manslaughter.The following morning, Judge Mary Theisen addressed the Olson family with watering eyes. She told them that Katherine's life had touched the entire courtroom.The sympathy turned to rage as her gaze fell on Michael Anderson. "You're a callous, cruel, and unjust human being," Theisen said, sentencing Anderson to a mandatory term of life in prison without parole.On an unseasonably snowy March 20 this year in New York City, George Weber—a passionate, affable 47-year-old radio newsman for WABC—posted a Craigslist ad looking for rough sex.His solicitation was answered promptly by 16-year-old John Katehis, a self-described sadomasochist and Satanist who lived with his separated parents in the East Elmhurst neighborhood of Queens. "I can smother somebody for $60," he wrote to Weber. In the context of what was to be a sadomasochistic romp, Katehis' aggressive reply failed to raise red flags.The two met in Brooklyn and made their way to Weber's first-floor brownstone apartment in Carroll Gardens. There, Katehis allegedly stabbed Weber some 50 times in the neck and torso. The teen stripped off his bloodied clothes, put on a clean pair of jeans and a T-shirt purloined from Weber's wardrobe, and hopped the G train back to Queens. When police arrested Katehis at a friend's house in upstate New York, he was still wearing Weber's clothes.About three weeks later, on April 14, Philip Markoff—a tall, blond 23-year-old med student at Boston University—came across an Erotic Services ad on Craigslist posted by 26-year-old Bronx-based call girl Julissa Brisman. Markoff sent her an e-mail, and the two arranged a soirée at the Marriott Copley Place Hotel in Boston's upscale Back Bay district. Seconds after entering the room, Markoff allegedly pounced on Brisman, who, according to a medical examiner, fought back tenaciously. Markoff stands accused of shooting Brisman three times—twice in the torso, once in the hip—killing her.Markoff was with his fiancée, on their way to Foxwoods Casino in Connecticut, when he was pulled over and arrested just south of Boston on I-95. The summa cum laude graduate of the State University of New York-Albany was later implicated in a similar Boston robbery, as well as one in Warwick, Rhode Island. A common thread ran through all three crimes: young women solicited through Craigslist's Erotic Services category.Even more than the Weber slaying, the Markoff murder captured the public imagination. How could somebody like Markoff—clean-cut, well-educated, ambitious, and in the midst of planning a beachside wedding this summer—do such a thing? Lacking any other hook, the national press dubbed Markoff "the Craigslist Killer," a phrase that still makes Newmark and Buckmaster cringe."We're taken aback any time we hear that term used," says Buckmaster. "Although if you stop and think about it, it's a testament to how exceedingly rare violent crime is on Craigslist, when you consider that it's the most common way that Americans are meeting each other these days by a significant margin. The reason they don't call him 'the Handgun Killer' or 'the Boston Killer' or 'the Hotel Killer' is because thousands of homicides have involved those factors."The Weber and Brisman murders couldn't have come at a worse time for Craigslist. Just as the crimes were splashing into prime-time news segments, a sheriff in Chicago was mounting a campaign against the company.Cook County Sheriff Tom Dart first made headlines in October when he announced he was suspending all foreclosure evictions in his jurisdiction. The energetic state representative–turned–sheriff was fed up with throwing law-abiding people out on the streets.By March, Dart was onto a new cause: Craigslist. He filed a federal lawsuit against the site, accusing it of "facilitating prostitution." He claims that during the past two years his department has arrested more than 200 Craigslist users on charges ranging from prostitution to juvenile pimping and human trafficking."In the hundreds of arrests that we've made, never have we had one where we went under the guise that it's a massage and it turned out that it was just a massage," says Dart. "We know what's going on."Despite Dart's confident tone, most legal experts believe his lawsuit has little chance of success; a clause in the Communications Decency Act immunizes Web sites from liability for content posted by third parties. The goal is to ensure robust free speech, says Matt Zimmerman, an attorney with the Electronic Frontier Foundation. "We don't want to have to make Web sites actively monitor what goes on, because that would drive up costs, and you would have every site saying, 'You know what, it's not worth it, we're not going to allow people to talk to each other at all.'"A far more imposing threat to Craigslist is Connecticut Attorney General Blumenthal, who last year convinced Craigslist to regulate more closely its Erotic Services category, but who resurfaced last month with additional, more sweeping demands. In an open letter, Blumenthal implored Craigslist, among other things, to disallow salacious prostitution-themed search terms, hire staff to monitor for pornographic images and ads, and eliminate the Erotic Services category altogether.Buckmaster says Craigslist welcomes the "constructive criticism," and confirms that the two sides are in the midst of hashing out a voluntary agreement. But don't expect Craigslist's most popular and controversial category to go away anytime soon."We added the Erotic Services category some years ago at the request of users who had been seeing those ads posted throughout our personals and services categories and wanted to see them collected in one space and put behind a warning screen," says Buckmaster. "And having them in one place has allowed them to be monitored more closely, by both our staff and law enforcement."Others in the online classified-ad trade back Buckmaster's assessment. Carl Ferrer, co-founder of Backpage.com, Village Voice Media's online classified partner, points out that even if Blumenthal's demands were met, it wouldn't safeguard against people posting such ads elsewhere."If you eliminate Erotic Services, the content will just migrate to Miscellaneous Services and other categories," Ferrer says. "Then it becomes a whack-a-mole strategy."There's also no evidence that overall rates of prostitution or murder have increased in correlation with Craigslist's ascent, says Zollman of the AIM Group. "There have always been hookers. There have always been people who sell drugs and other illegal things. But to call these 'Craigslist-related crimes' is no fairer than calling car accidents 'GM-related deaths.'"Even the Olsons are sympathetic to Newmark. Speaking recently in their Cottage Grove home, family members talk about their disgust with the 48 Hours Mystery episode they'd watched the night before. The show, "Craigslist: Classified for Murder?" nags at Sarah. It hurt her to see a full hour dedicated to bashing a company that's helped her family so much."There are evil people out there," says Sarah. "And unfortunately, Craigslist is built for everyday people. And so someone that has ill will, someone psychotic, like Michael Anderson or this medical student, they are going to take it for what it is worth. It's a free tool and they will take advantage of it. And evil people will take advantage of whatever they can."This past Sunday, about 700 of Katherine Olson's friends and family gathered at Grace Church, a colossal house of worship in Eden Prairie, about 15 miles southwest of Minneapolis. The last time this group had been together was at Katherine's funeral, but this day they eschewed black clothing in favor of pastel-colored spring attire. There were no tears among the congregants, no Kleenexes hastily passed. This was to be a day of celebration.When it came time to begin, five members of the Olson family took the stage to subdued applause. Trailing behind in a black suit worn over a tieless maroon dress shirt was Craig Newmark. After a brief introduction by Sarah, Newmark approached the podium, grabbed the microphone, and leaned over his prepared remarks."I am really, really humbled and really honored to have been invited here today to speak at this tribute to Katherine, extended by the whole Olson family," Newmark told the crowd. "I was personally sickened and horrified when I heard about this tragedy. I started Craigslist around 14 years ago as a way to give back to the community."Rolf stood behind Newmark, gazing thoughtfully at the crowd."Despite the billions of times well-meaning people have helped each other through Craigslist, it's been devastating to see that it can also be used by bad people to take cruel advantage of others and bring a senseless end to a beautiful young life," Newmark continued. "The most recent crime in Boston has been a grim reminder of that."It became clear he wasn't speaking just on behalf of Katherine, but also on behalf of reason and personal responsibility in the age of the Internet."I'm saddened that we met under these circumstances, but I am truly inspired by the Olson family and I extend my love and friendship to them," Newmark concluded. "And I applaud everyone's effort to let Katherine's light continue to shine."