Rene Ritchie at TiPb recently noticed that Apple's new Game Center seems to be capped at 500 friends, which another user was able to confirm.
After receiving 500 friend requests*, Rene noticed they stopped coming in. He figured that was the end until he saw a tweet from fellow Game Center user MuscleNerd:
"So much for my not-so-secret plan to break GameCenter! They're capping my friend count at 500 (as soon as I delete 1, I get 1 new request)."
After some testing, Rene confirmed the same thing. As soon as one request was deleted, another popped up. So, if you've got a lot of requests waiting beyond 500, you won't see them. As Rene