Why Steven Sinofsky is out at Microsoft - Several plausible reasons
arstechnica.com
arstechnica.com
Of course, this is just speculation.
http://allthingsd.com/20121113/in-the-sinofsky-departure-bil...
Basically Sinofsky was fired because Ballmer/Gates wanted more collaboration/integration between the other divisions. And Sinofsky is famous for protecting his fiefdom. Very similar to Forstall.