Revelations this week that Facebook received data about users' Web-surfing activity, even when they were signed out of the service, prompted two lawmakers to complain to the Federal Trade Commission.
"When users log out of Facebook, they are under the expectation that Facebook is no longer monitoring their activities," Reps. Ed Markey (D-Mass.) and Joe Barton (R-Texas) wrote to the FTC on Wednesday. "We believe this impression should be the reality. Facebook users should not be tracked without their permission."
Markey and Barton, who co-chair a bipartisan privacy caucus in Congress, are asking the FTC to probe whether Facebook engaged in an unfair or deceptive trade practice.
Earlier this week, Australian developer Nik Cubrilovic wrote on his blog that Facebook received information about users whenever they visited sites with widgets, such as the "Like" button. Cubrilovic reported that the data is transmitted even when users are logged out of the social networking service.
"The only solution is to delete every Facebook cookie in your browser, or to use a separate browser for Facebook interaction," Cubrilovic wrote on Sunday.
Facebook acknowledged that it received data about logged-out users, but said it did not store that information. The company said on Tuesday that it had fixed the "bug" that allowed it to learn when logged-out users visited sites with the Like button and other widgets.