I only use Facebook, and I've got about 250 friends. And they are, at least, real world acquintances. So, not random people I met once! Or never met...

Yeah, having people you don't actually know being friends freaks me out. I mean, there's hundreds of photos of me on Facebook, and I should let some stranger be able to access them, just because they want to be my friend. And it's not like you can actually check them out and see that they're alright. No, my friends on Facebook will remain people who I actually know.

EDIT: As I was writing this, some stranger has friend requested me.