I wonder if John Carmack wouldn't be better off just launching a competitor to Oculus. Wherever he goes the magic will follow, and it'd be nice if he was the ultimate boss like he was at id Software.
I'd just really hate for him to get bogged down in a bad environment, kind of the way Linus did with Transmeta, and be forced to resign at some point and start over after wasting years of productivity.
The A16Z guys can probably help avoid any massive stupidity, so that's a nice benefit to this investment.