The brutal killing of 25-year-old Julissa Brisman in Boston earlier this month has raised questions about Craigslist's role in facilitating serious crimes, however inadvertently.
In an exclusive interview with Martin Bashir, Craigslist founder Craig Newmark spoke for the first time about the latest Craigslist-related murder, expressing compassion for the victim.
Watch the story on "Nightline" tonight at 11:35 p.m. ET.
"My first reaction is sympathy, I mean I feel pretty bad for the victims and their families. I don't like it at all. Beyond that, well, how would you feel if ... the bad guy watched what you do on TV and started calling [you] the 'ABC Killer?' That's pretty much how I'm reacting," Newmark said. "It just feels bad. You know, remember, I'm spending a great deal of time here fighting bad guys."
Philip Markoff, 23, was arrested Monday and charged with Brisman's murder. Police say he contacted her through a Craigslist ad offering exotic massage services.
Markoff denies all the charges, but police say there's ample evidence linking him to the crime, including plastic restraints similar to those used in the murder, a gun found in his apartment that allegedly links him to the shooting and even the underwear of the victim. Markoff is now sitting alone in a Boston jail cell, on suicide watch.
Craigslist is now one of the most-visited Web sites on the planet. Newmark's online service allows users to post advertisements for everything from yard sales to massage services. Every major city in America has its own Craigslist, and there are hubs overseas. Most of the postings are free, and there are separate sections for jobs, apartments and social events.
But there are also sections called "Casual Encounters" and "Erotic Services."
Many in law enforcement believe these sections involve the brazen promotion of prostitution.
The site has been criticized by Massachusetts Attorney General Martha Coakley and Connecticut Attorney General Richard Blumenthal. "Craigslist is the largest source of prostitution in America," said Cook County Illinois Sheriff Tom Dart.
Newmark, however, disagrees, telling ABC News that his site does not facilitate prostitution.
"Sometimes a bad guy of some sort tries to pull a fast one on our site. We don't want it there, it's wrong, and that's why we have the help of the general community and the law enforcement community getting rid of things like that," he said.
Prostitution aside, the site was linked with several violent crimes in recent years.
This month Michael Anderson was found guilty of shooting a woman to death lured to his apartment by a Craigslist ad. Earlier this year New York radio reporter George Weber was stabbed 50 times in his Brooklyn apartment, murdered by a man who answered Weber's ad on Craigslist offering $60 for "rough sex." In January Willie Donaldson was indicted for fatally shooting Michael Hicks, a man he met on Craigslist in Arlington, Virginia. Donaldson's attorney argued that his client fired at Hicks in self-defense.
Craigslist CEO Jim Buckmaster said the 50-million strong Craigslist community has a low incidence of crime.
"Now the risk is not zero, and no occurrence of violent crime is acceptable," Buckmaster said.