My theory:
Well we all remember what happned to the guys and gals that played borderlands, forza and ODST early. WELL notice what M$ told us, they said that these people where playing illegal copies of the game, and that people that were playing legit copies are ok and safe ..... i.e. it doesnt have to do with playing the game early.... it seems M$ knew/know how to tell that your palying a burnt game.
As soon as wave 4 games hit, so basically a day before/after halloween, mass bannings occurred (M$ knew all along). Anyway this is just pure M$ fashion, banning everyone before a major dashboard update that is the facebook, last.fm and twitter
Im sure many of us remember the bannings last year that occured to people when they tried to update from pre-nxe to nxe.... meh they knew all along, we were jsut too blind to see it.