Quietly -- or not so quielty, depending on your perspective -- the XBox has become a behemoth in the entertainment world. Not just with video games, but with all forms of entertainment content (aside from music, which MSFT has never really been able to nail). Take, for instance, the interesting stat that over 60% of all Netflix streaming users stream via a gaming console. Or that close to half of all XBox owners watch one hour or more of TV or movie content per day through their consoles. Though it has formidable competitors in Amazon, Apple, and to some extent Google, Microsoft has a pretty impressive strategic position in the battle for the living room.
The only chink in the armor has been mobile. That's why MSFT kept investing so heavily in Windows Phone, and why it's going to fight as hard as possible in the tablet space. Not owning mobile means not owning the total entertainment experience, which means not having a ubiquitous ecosystem. So mobile is pretty darned crucial here.