Craigslist made a splash last month when it announced a set of policy changes aimed at stamping out sex crimes facilitated through the Erotic Services section of its site. But sex workers and legal experts say the measures are likely to have scant impact on the shadowy world of online prostitution.

Following the initial report about the new policies, a reader who identified herself as a "working girl in San Francisco" told InternetNews.com that Craigslist is hardly the only game in town.

"Because of the new procedure on Craigslist, we are turning to other Web sites ... to promote our services," she wrote in an e-mail. "These sites are free and just as effective. I don't believe that this change in Craigslist will do anything to affect the industry."

The reader declined to be interviewed further for this report, but people on both sides of the war on prostitution agree that the multiplicity of adult-oriented sites on the Internet has made the policeman's work considerably more complicated.

"It's really just a function of today's digital economy," said Alexander Southwell, an attorney with the law firm Gibson, Dunn and Crutcher and a former federal prosecutor. "The Internet's ability to make illicit services available is really groundbreaking."

"It's a question of convenience," Southwell told InternetNews.com. "It used to be for prostitution you would have to go to some shady corner of town at night. Now you can do it on the Internet."

In partnership with more than three dozen states' attorneys general, Craigslist recently began requiring advertisers to provide a working phone number before posting an ad to the erotic services section. It also started charging a $5 dollar fee, which entails credit card verification, for the erotic ads that users had previously been able to post for free.

The effort follows previous initiatives between state law enforcement agencies and social networking communities MySpace and Facebook to expel sexual predators from those sites.

Craigslist pledged to coordinate with law enforcement officials from the participating states, and has filed a series of lawsuits against companies it believes are providing software to enable people to evade its usage policies.

But Craigslist is just the tip of the iceberg, according to Connecticut Attorney General Richard Blumenthal, who spearheaded the initiative.

"If you take the sex trade internationally, or even nationally, Craigslist is a pretty small part of it," Blumenthal told InternetNews.com. "We're beginning with Craigslist because it's the biggest and one of the most apparent -- and frankly, one of the more cooperative. They've been cooperative from the early stages of our investigation."

That investigation, which in addition to prostitution is probing other crimes such as child exploitation and human trafficking, began early this year.

"We're reviewing other sites, and we're beginning a dialogue with them," Blumenthal added. "My hope is that others will [cooperate] as well."

As part of its effort to purge illicit sex ads, Craigslist is deploying software and filtering tools to remove ads with pornographic content from the erotic services section. Craigslist did not respond to a request for comment for this story, but Blumenthal noted that that effort is still in its early stages. In addition to the pornographic images of men and women that can still be found in the section, it also contains ads with warnings about the new enforcement policies and links to other adult-oriented sites.

Reliable statistics on the scope of the industry -- particularly the online segment -- are difficult to come by. Blumenthal admitted that there is "no way of determining" the extent of the online sex trade.

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