• by Wendy Davis  @wendyndavis, July 17, 2009

Craigslist's recent decision to replace its "erotic services" section with monitored "adult services" listings has not stemmed prostitution ads on the site, Chicago Sheriff Thomas Dart is arguing in a lawsuit against the site.

"Craigslist is the largest source of prostitution in the country," Dart alleges in recent papers opposing Craigslist's request that the case be dismissed.

Dart sued Craigslist in federal district court in Illinois in March, arguing that the site creates a nuisance by facilitating prostitution. Dart requested an injunction against the site and monetary damages.

Craigslist filed a motion asking U.S. District Court Judge John Grady to dismiss the case on the theory that the Communications Decency Act immunizes Web sites from liability for unlawful ads created by users.

But Dart now argues that Craigslist doesn't just serve as a forum for ads, but helps develop the unlawful listings on the site. "Third party users did not create an adult services category on its Web site; Craigslist did," Dart argues. "Third party users did not create the forum's word search function; Craigslist did."

Many courts have held that the Communications Decency Act protects Web sites from liability when people use the sites to commit crimes. But Dart points to some recent decisions that seem to chip away at that protection. In one somewhat similar case, the 9th Circuit Court of Appeals ruled that Roommates.com could be sued for discriminatory ads because the site actively solicited unlawful information.

But the 7th Circuit, which covers Chicago, ruled in a separate case that Craigslist wasn't liable for illegal housing ads placed by users.

Craigslist has been under intense scrutiny for its ads this year, much of it triggered by the murder in April of masseuse Julissa Brisman. She was allegedly killed by a Boston University student who answered Brisman's ad on Craigslist's "erotic services" section.

In May, Craigslist launched a new "adult" section, where posts are screened in advance to weed out blatant prostitution ads.

Craigslist says on its site that ads "suggesting or implying an exchange of sexual favors for money are strictly prohibited."

But Dart argues in court papers that the site still includes illegal ads. "The new adult services section is thriving and its posts confirm what is being offered, sex for money," he alleges.

Craigslist also is involved in litigation in South Carolina. There, Attorney General Henry McMaster had threatened to bring criminal charges against Craigslist executives for aiding and abetting prostitution. The site filed a lawsuit against McMaster, and in May, obtained a temporary order preventing him from prosecuting company executives.