Facebook Friends

I like Facebook, other than the fact that it is a total time waste and somewhat voyeuristic. But what are the rules regarding friends? I have a couple hundred friends I think, most of which I personally know or knew for an extended period of time. Others are more like acquaintances. Two such incidents are former significant others of my siblings. So, what do I do about that? Leave them as friends? I didn't break up with them after all, and I actually really liked both of them and would have no problems carrying on a conversation now with either one of them. Part of me just thinks it is weird! Any thoughts?