Craigslist has become a "cesspool of crime" and has been linked to 20 murders in the past three and a half years, according to a research firm commissioned by a competitor. A report released Thursday by AIM Group claims 330 crimes have been linked by law enforcement to the site, which allows users to post free online classified ads. Among those are the victims of the so-called "Craigslist serial killer" that has recently been targeting prostitutes on Long Island, N.Y. "Sadly, Craigslist has become a cesspool of crime," said AIM Group founder Peter Zollman. Craigslist CEO Jim Buckmaster responded on...