Most of the time I don't even notice. If I do notice, I don't really care. It's slightly irritating when it's someone who sent me a friend request and then a couple months later they unfriend me. It's like, why did you even add me in the first place? But really, I don't care. There's only a handful of people I kept in touch with after high school and no one from college is on my Facebook. So it doesn't matter.