In the lawsuit, quietly filed last week, Dallas County resident Cathryn Elaine Harris claims that Blockbuster violated the federal Videotape Privacy Protection Act by sharing information about her movie rentals and sales with Facebook without first obtaining her written consent.

Harris is seeking class-action status, and is asking for at least $2,500 for each violation of the statute, a 1988 law passed after a newspaper obtained the video rental records of U.S. Supreme Court nominee Robert Bork.

When Facebook launched Beacon last November, the platform told members about their friends' e-commerce activity at Blockbuster and other sites. Initially, the program operated by default, meaning that unless members opted out, their rental information was sent to other Facebook users as part of Facebook's ad program. Harris alleges that this type of ad violated the federal video privacy law.

Four weeks after the program launched, Facebook revised it to require users' opt-in consent before sharing information with other members. But the Beacon platform still allegedly transmits information about people's activity from Blockbuster to Facebook, unless they have checked a box telling Blockbuster to never send such information. Harris alleges that such behind-the-scenes transmission also violates the act. "To this day, Blockbuster online members remain unsuspecting victims," Harris charged in the complaint.

This lawsuit appears to be the first one stemming from Facebook's Beacon program. But the platform caused massive public relations problems for the company. Last November, more than 50,000 members joined a protest group created by MoveOn, dubbed "Petition: Facebook, stop invading my privacy!"

Facebook CEO Mark Zuckerberg last December apologized for how the company launched the platform. "We've made a lot of mistakes building this feature, but we've made even more with how we've handled them," he wrote on the company's blog.

Facebook's Beacon involved more online retailers than Blockbuster, but U.S. laws provide especially strong privacy protections for people who rent or buy videos.

"The Video Privacy Protection Act is an important privacy law that safeguards the information of individual who rent movies," said Marc Rotenberg, executive director of the Electronic Privacy Information Center. "If they disclosed information that's protected under the act, obviously there are going to be some real claims here," he added. The Electronic Privacy Information Center isn't involved in Harris's lawsuit.

Blockbuster spokesman Randy Hargrove denied the allegations. "Our alliance with Facebook included numerous levels of privacy protection built in for our online subscribers," he said. "While we cannot discuss the specifics of this lawsuit, we intend to vigorously defend the company in this litigation."

Facebook declined comment on the lawsuit.