Mac Rumors reports that iOS 4.1 Beta 3 supports no longer game center on the iPhone 3G and the 2nd Gen iPod Touch

Amongst the changes to the developer release of iOS 4.1 last night, Apple has removed support for Game Center on the iPhone 3G and 2nd generation iPod Touch.

  Game Center Drops Support for iPhone 3G and 2nd Gen iPod Touch in iOS 4.1 Beta 3