Wow, I think someone noticed another one of my character flaws. Almost every relationship in my life has ended this way. I haven't lost many people to death (something I am deeply grateful for); I haven't parted ways with someone after an intense argument revealing "irreconcilable differences" and considering the amazing ability we have through technology to keep in touch with anyone, anywhere, I can't honestly say I somehow "lost contact" with someone. I could probably find them on facebook if I really wanted.
So drifting is the way in which I tend to lose people. Any close friend from high school would make the list of drifters. I tried to convince myself that graduation wouldn't mean good-bye, but once I had been gone a couple years, I realized how little I had in common with those friends. I think we were merely united by experience. We witnessed the same bullying, listened to the same teachers, and struggled through the same assignments. After school, however, we had different experiences which changed us just enough so that we can no longer relate the way we used to.
Most college friends have drifted too. I had several roommates, but keep in contact with just one. Considering also that I was in 4 weddings due to college relationships, it's sad to think I have seen only one of those friends since (although I am not counting subsequent weddings). All in all, I keep up with 3 friends from college - a small number considering how close we once were. Again, I think we were united by situation and I just naturally clung to the people with whom I genuinely share similar interests.
If I'm close to family, it's because they insisted. My mother's family has this ridiculous habit of staying connected. They have made it a priority so it has happened. (Quick example: When I was asked out for the first time I got a call within a couple hours from my grandpa congratulating me. He had heard it from my grandma, who had heard it from my aunt, who had heard it from my other aunt who had heard it from my mom whom I had told, emphasizing that it wasn't a big deal. Did you follow that? Information travels fast.) You can't drift away from the family - they would never let you.
Again, I guess I wasn't specific, but I'm not much for naming names.