You can now view and manage the top 100 scores and usernames for all of your Game Center leaderboards. Protect your legitimate players by signing in to iTunes Connect to delete fake scores or block players that post fake scores. You can also restore scores and players within the same time period. To learn more, read the Managing Game Center Leaderboard Activity section in the iTunes Connect Developer Guide.
So if you someone posts a 100pt win in a soccer match, rest easy, the red card is on its way.
(Seriously, though, how often do you see fake scores in Game Center?)