• by Wendy Davis  @wendyndavis, June 18, 2010

Facebook was hit with another lawsuit this week alleging that it improperly shared users' personal information with advertisers.

This case, the third such lawsuit in as many weeks, was filed in federal district court in Rhode Island by North Providence Facebook user Wendy Marfeo, who is seeking class-action status.

As in the otherlawsuits, she alleges that Facebook violated its privacy policy by sharing users' names with advertisers via referrer headers. Marfeo alleges that Facebook broke its contract with her and also violated federal wiretap law.

The allegation that Facebook was sharing information with advertisers first surfaced last summer, when two computer scientists from AT&T and Worcester Polytechnic Institute published the report, "On the Leakage of Personally Identifiable Information Via Online Social Networks."

The researchers concluded that many social networking sites "leak" personally identifiable information by including it in the HTTP header information that is automatically sent to ad networks. A Facebook spokesperson said at the time that referring URLs only provided information about the profile page a user had been on when he or she clicked on the ad, but didn't necessarily reveal the user's identity. But Harvard professor Ben Edelman said last month that Facebook automatically embeds a profile tag in referring URLs when users view their own profile pages.

"We believe this complaint is without merit and we will fight it vigorously," a spokesperson for Facebook told Online Media Daily.

The social networking site faces at least five privacy lawsuits, including one that focuses on all revisions to the site's privacy policy since late last year and one that just focuses on "instant personalization," the new program that automatically shares users' names and other information with Microsoft Docs, Yelp and Pandora.

But one hurdle for all the plaintiffs is that they will likely have to show how they were harmed by the alleged data breach to prevail in a lawsuit.