Personally, I hate facebook. I don't care about what anyone is up to. If it's important enough, they'll let me know. You know, actually talking, face to face. People that feel the need to inform everyone they've ever known that "oh no, I just fell in the mud. Here's a picture of my muddy jeans", are, in my opinin, very sad individuals that very seriously need to find a life. I don't want to know what onspirational lyrics you've just found, or what half-arsed quote you think applies to your life, or how excited you are to see your boyfriend. I have just over 100 'friends' on facebook, and I've hidden about half of them simply because I really don't care about what is going on. The only reason I don't delete them at all is because it would cause drama, i.e. deleting workpeople would cause conflict in the workplace.
Which forces me to interact with these people outside of the usual environment, e.g. work, sport, uni, etc. I don't want to talk to my work people once I'm at home. Once I leave the workplace, that's it, I focus on a different situation in my life and don't worry about that one until I return. It wouldn't faze me one bit if I never see certain people again.
I think my main gripe is that I don't feel the urge to tell everyone what is going on in my life. Those that are actually important to me (friends, family) will know anyway, because I'll physically tell them. Everyone else doesn't need to know. For that reason, I never post on facebook.
And what is with those 'like' pages. "There's a page for brushing my teeth when you wake up? I do that!" *like*. It's absolutely pointless.
That said though, I do find it useful for organising events. Other than that, I hate it.