It's not a far leap of logic with all the other things Microsoft has paid to get exclusive this gen. MS is pretty much close to scum with the way they buy out developers for content this gen, imo. Prior to this gen, if things weren't available on one platform over the other, it was due to developer choice or publisher dictate (Nintendo censorship), not the platform holder handing over a bundle of $100 bills to developers to secure support for their borderline defective console and keep it's sales high.
we all have opinions - we all have platforms we prefer for various reasons, no need to call anyone names. But to me given what Xbox has provided "me" the gamer with this generation, A unified online system - reward program (achievements), great triple A titles, tons of DLC content, etc. seems most developers are approaching MS/Xbox (Square - Kojimo for example - or maybe MS went after them? i don't know, point is they got em) and then asking themselves, how can we innovate our game ideas on this platform, case in point HMX & Rock Band Network.
Xbox Live/PSN - iruhlman
Rock Band Network