I have some sympathy for social networking sites that, in order to become profitable businesses, must make use of the user data that is, in essence, the only asset these businesses have. Well, that and the goodwill of their users, which is sorely tested by the clumsy processes by which changes to user agreements and terms of services are made. What I don't sympathize with, in other words, is bad PR.
Facebook is by no means the only bad guy in that department.
For details, see: "Note to Silicon Valley: How Not to Handle Privacy."