To go back to the mobile analogy, I don't think Google chose to not compete on iOS vs the App Store. It's a large possibility that Facebook would be willing to lock down Oculus for more profits and Facebook has shown it wants to play hardball. I don't think developers would be able to ignore the Oculus demographic and they would be forced list their games on the Rift store.
That would kill new Oculus sales. Sure if Facebook gained a monopoly they would do all kinds of shady things, but there is little evidence that's going to happen.
