When I joined facebook in '04, it actually seemed like they cared about privacy. They had reasonable privacy controls, they made it easy to establish how much privacy you wanted on your profile, and they hadn't started selling ad-space of any kind, nor mentioned what their business model would really be. Unfortunately, by the time they began changing, selling user info etc., *everything* at school ran on facebook. *everything*. You couldn't be involved in student government, either as an official or just as a constituent, without being on facebook. Half the list-servs on campus, any clubs basically, switched over to facebook group messages. Saying you could do without facebook was essentially saying "you can take the entire social aspect of college and remove it. You can move off campus and never speak to any of your friends or be involved in any club or anything." If you had to ask about a party, it was assumed you hadn't been invited deliberately, not because you weren't on facebook. It was even worse when I was in school in England.
Being out of college, I avoid facebook like the plague. I sign in once every month or two. However, I get tagged in photos, websites, messages, etc at least once or twice a week, if not every day. And I can't just cut it off. There's a documentary who's production I've been following who didn't set up a website until a few weeks ago and which hasn't been updated since. It's for sale, but you could only find that out through facebook (I think they did actually update yesterday or something, so now you can get it at their website, I just checked.)
I too value my privacy, and find facebook to be the finest example of everything wrong with capitalism. Unfortunately, because of the power they wield in the sheer number of users, I can't be rid of it even if I decided to give up all those facebook only things (like the documentary) thanks to tagging, etc. I'm idling until either a) facebook does somehting really, really stupid (which I can't even fathom how stupid it would have to be for people to leave) or b) I can start help making diaspora an alternative for my friends and, eventually, all the things I find useful knowing about.