What this all really comes down to is the almost instant ubiquity of the "Like" button. (You may have noticed that your Facebook friends seem to be "liking" more lately.)
So, is this all cool with you? Maybe, right? Personally, I think the automatic opt-in is a little presumptuous (if not downright scary), so instead of clicking through, I actually check to see how Facebook is using me. (Full disclosure: I agree with Molly Wood when she says "I hold few illusions that Facebook's business strategy has ever been about anything other than building up a huge user base and then selling ads to those users." That said, I am also a pretty avid Facebook user. "Hypocrite auteur!")
Short of entirely deleting your Facebook account, you can actually protect yourself quite well. Here's a decent (and short) video on how to toggle your privacy settings:
For all you "reading types" out there, here are (one, two) text-based guides to protecting your privacy.
Oh, and apparently this whole thing has gone political, with some Senators making noises about the new initiative.