Dear 100 Hour Board,
Why would an ex unfriend you on facebook a year after he broke up with you, but not the other 2 girls he dated and broke up with since then?
If your ex is anything like me, he unfriends anyone who isn't part of his life anymore. One criterion that I personally use to judge whether I keep someone as a friend or not is "Have I seen or had any communication with this person in the past year?" If the answer is no and there isn't any other reason to keep them as a friend, then I unfriend them. I'm sure the vast majority of them don't notice, because they were mostly acquaintances in the first place.
On the other hand, maybe it's not just a routine unfriending session. Maybe he's trying to help you, because you seriously need to move on with your life if you're still keeping track of whether he's friends on Facebook with the girls that he has dated since you broke up. Like, maybe tone it down a little?