A few months ago, jaws dropped as Facebook shelled out $2 billion to purchase Oculus VR, a virtual-reality headset company started on Kickstarter. Nobody knew why the social network had acquired this cyberpunk technology company. That was, until last night at the Techcrunch Disrupt conference, where Oculus CEO Brendan Iribe revealed what many of us thought might be too sci-fi to simply assume: Facebook would like to build the first billion-person game...