I'm also worried about this outcome. However, John Carmack is on the record as being an extremely outspoken opponent of software patents. He's also a smart guy

I'm also worried about this outcome. However, John Carmack is on the record as being an extremely outspoken opponent of software patents. He's also a smart guy. So, chances are a) he's already thought of and discussed the patent issue with FB, b) FB aren't intending to own the entire VR sector with patents (or at least, if they are, they did a damn good job of lying about it) and c) any attempt by them subsequently to patent everything that's not nailed down will have considerable internal resistance. None of this rules out the "FB patents key elements of VR, VR is screwed" scenario, though.