The debate intensified earlier this week after a Boston University medical student, and arraigned earlier this week for allegedly murdering one woman and kidnapping and assaulting another - both of whom he found in erotic services . The attacks and subsequent arrest have put the spotlight on a Web site that lets people post ads selling old sofas and bicycles, along with escort services and massages.

But while some say that Craigslist, which does publish on its site, succeeds in being a free and open marketplace, others say some of the ads under its "Erotic Services" category go too far legally. And the question, since prostitution and advertising for such services are illegal in most states, is whether Craigslist could find itself in legal hot water.

Seems Cook County Sheriff Thomas J. Dart would think so.

Last month, Dart filed suit in U.S. District Court against the , accusing them of knowingly promoting and facilitating prostitution. This came just four months after the Web site settled a national lawsuit, vowing to set up safeguards to restrict some postings on the Web site.

"Craigslist is the single largest source of prostitution in the nation," contended Dart, who is asking a federal court to order Craigslist to eliminate its "Erotic Services" section. "Missing children, runaways, abused women and women trafficked in from foreign countries are routinely ... being pimped on Craigslist."