Just a few minutes ago in another comment i was writing on joystiq, i attested to the fact that, much like the "kiddie" stigma haunts Nintendo, the "Frat Boy" stigma might haunt Microsoft if they really start to try and move 360 further into the mainstream (as in, a product for everyone, and not just the mainstream gamer). There is already a certain dissonance that comes with seeing games like Banjo Kazooie, Viva Pinata and such on 360. Granted, the stigma didn't hurt VP's sales too bad, though it did kinda hurt BK (though BK arriving in an incredibly oversaturated market might've helped)
I dunno. It might just be marketing BS, but it might have some substance.