An article (available online) from the June 2012 issue of Consumer Reports reports on Facebook, its users, and privacy issues.
From the Article
Some people are sharing too much. Our projections suggest that 4.8 million people have used Facebook to say where they planned to go on a certain day (a potential tip-off for burglars) and that 4.7 million “liked” a Facebook page about health conditions or treatments (details an insurer might use against you).
Some don’t use privacy controls. Almost 13 million users said they had never set, or didn’t know about, Facebook’s privacy tools. And 28 percent shared all, or almost all, of their wall posts with an audience wider than just their friends.
Facebook collects more data than you may imagine. For example, did you know that Facebook gets a report every time you visit a site with a Facebook “Like” button, even if you never click the button, are not a Facebook user, or are not logged in?
Your data is shared more widely than you may wish. Even if you have restricted your information to be seen by friends only, a friend who is using a Facebook app could allow your data to be transferred to a third party without your knowledge.