Microsoft is buying their way into the market. I have no doubts or reservations about this fact. Buying exclusive content, paying to get a game on their system and advertising are just a few of the legitimate ways they are doing so.
The real question is how much of their money is going to sabotage efforts of the other consoles?
Microsoft has long been known for shady business practices and I wouldn't put it past them to have manufactured some of these glitches in PS3 and Wii versions of game that are multiplat. (The real question to me is how much did they pay Activision to fuck up GH3 and Rockband?)
I think that this type of thing is abhorent (not to mention illeagal) and I become more certain that this is happenening each time a new glitch or missing feature appears that doesn't affect the 360 version.