Facebook's funny. In about five years it has transformed from a larval collection of collegiate address books to a network for anybody, anywhere to say just about anything. The changes in between have been subtle and blatant, but ever-present tweaks have been the status quo for the hate-the-term-but-what're-ya-gonna-do social network.
Instead, there is but one foolproof way to handle this: don't ever — EVER — put something online that you wouldn't want the whole world to know. Ever. End of story. (But not end of article.)
Blogger Kenneth Yeung has a refreshing analysis of how these websites just don't give a shit about privacy. Maybe they don't believe in it. Or possibly they consider online privacy to be negotiable. And you may disagree, but I don't believe in it either.
The Internet is not anyone's private playpen. It never has been, and it never was. Your friends have always been sharing your e-mails, your IMs, and your tweets to other people ... perhaps even to those who can't fucking stand you. Breach of privacy! UNSUBSCRIBE FROM THE INTERNET!!1! (But your friend is still cool.)
So far I haven't read about any egregious invasion of privacy. I haven't heard about any users opting out of a program then still had their information disseminated to other companies. And I'm pretty sure no credit card numbers have been leaked to potential online flimflammers.