Only reason for MS to go after Valve or EA would be to make them X-Box exclusive, or get bored of them and then shut them down a year later. Valve's a non-starter as it's private and already Gabe's own project that can do anything it wants (or not). EA is a goddamn mess, and I wouldn't be sad to see the management thrown out. However, with MS, we could easily lose all of EA's IP to Xbox only. Looking at their past, we could also see MS getting bored, decide that a big foray into games is no longer what they want, and shutting it all down just because they have the money to do it and not care. It would be ironic for MS to do to EA what EA have done to countless studios ie buy them and burn them down.