"You already know that Facebook and privacy don't really get along, but many "improvements" to the service are making it easier and easier to share everything without even knowing. Avi Charkham rounded a bunch of these tricks up over at TechCrunch, and they're as subtle as they are sketchy.
Some of the changes seem to play on psychology, like swapping out the old pair of "Allow, Don't Allow" buttons for just one that says "Play game" that you either click, or don't. Others, are sort of flagrant once you've noticed them. One Charkham describes as the "The Tiny Hidden Info Symbol Trick" is of those ones."