Though Facebook's hostile attitude toward user privacy would by itself be enough to keep me away, these types of issues are the kind of thing that makes me sour on the notion of social networking entirely, not just Facebook's specific implementation thereof. I know there are also many benefits, but I think the casual nature of the medium, and the relative ease with which people can stay "connected" without really communicating in depth, biases most conversations toward the trivial. (Disclaimer: I don't have a Facebook account, but my wife does, so I've experienced it as a spectator.)

I look at it this way. Back in the day when I ran a dialup BBS and dialed into dozens of others, staying connected with a circle of online friends took effort, and was therefore more focused. Which BBS you dialed into depended on who you wanted to talk to, or what you wanted to talk about, and when you'd had enough of that, you'd log off and hop to another destination that had a different set of offerings. Online forums try to replicate this, with varying degrees of success. (Obviously this one does a better job than most.)

With Facebook, it's one-stop shopping for all your communicating needs. That's good for posting a funny link or saying "Hey I'm in Albuquerque for a weekend, where's a good place to get a beer?" but not so good for things like an in-depth political conversation. It's not that it can't happen, but I think there are many factors working against it on Facebook.