But how much of who you are do you really want to share, and with whom? Two congressmen and 10 public advocacy groups have now urged the Federal Trade Commission to investigate whether Facebook tracks users' online movements even after they log off the site. A class-action (Davis v. Facebook) has been filed as well in Federal District Court in San Jose, Calif.
Reps. Ed Markey, D-Mass., and Joe Barton, R-Texas, co-chairmen of the Bipartisan Privacy Caucus, wrote to the FTC: "We believe that tracking users without their knowledge or consent raises serious privacy concerns. When users log out of Facebook, they are under the impression that Facebook is no longer monitoring their activities. We believe this impression should be the reality."
Facebook said the issue was overblown. The social media behemoth did concede, though, that it found that three of its "cookies" -- small files a website leaves in your computer when you visit -- "inadvertently included unique identifiers when the user had logged out of Facebook," according to Andrew Noyes, Facebook's manager of public policy communications in Washington. "However, we did not store these identifiers for logged out users," he said in an email to ABC News.
As for the lawsuit, "We believe this suit is completely without merit, and we will fight it vigorously."
Facebook's explanation of what happened didn't go over well with EPIC, the Electronic Privacy Information Center, which has often locked horns with the managers of major websites. It said Facebook was using "supercookies" -- more troublesome than the regular cookies used by most commercial websites.
EPIC said Facebook did not take any action until an Australian blogger, Nik Cubrilovic, posted about the tracking after a year of questioning the company about it. And it said the new Timeline and Ticker -- which Facebook hopes will allow "frictionless" sharing with friends -- may cause users accidental embarrassment, even if the company means well.
"It is difficult for users to keep up with Facebook's frequent changes and adjust their privacy settings accordingly," said David Jacobs of EPIC, "and the company has not clearly explained what it plans to do with the wealth of new user information that will be collected as a result of the new applications."
All this has become a war of words. On the one hand, there have now been countless cases in which people inadvertently shared things on social media sites that they later regretted. Would you want some future employer to see pictures from that party you went to Saturday? Do you know what settings would prevent that?
On the other hand, what's the harm to most people if a website knows your interests? That they'll show you ads tailored to your preferences?
"Some groups believe people shouldn't have the option to easily share the songs they are listening to or other content with their friends," said Facebook's Noyes. "We couldn't disagree more and have built a system that people can choose to use, and we hope people will give it a try."