This has probably been suggested before but how about a system that bans all regions (as well as proxies) except the one where a legitimate user is ? It would certainly be a better solution than banning a player who has purchased the game.
How to feck up a perfectly good game:
UT (1999) = UnbelievableGameSoCoolIMustHelpBringNewPlayers Tournament
UT (2008) = Unreal ThrustMyPrivatePartsInYourFaceBish
And that's probably why UTIII was a relative flop. New game, same sh*thead players ^^.