This is reminding me a little too much of the backlash when Disney bought Marvel, and I have a similar response to this.
It's very unlikely that Facebook is going to make huge changes to the way Oculus operates, as well as the audience that it is targeting. That's probably the worst thing they could do actually, they'd risk alienating the entire target audience if this VR tool was turned into an extension of social media. A lot of the horror stories that I'm hearing from people who oppose this change are scared of what could happen. Well, there's a lot of things in this world that could happen. Disney could have turned Marvel properties into ultra kid-friendly shadows of their former self, but for what gain? The people who were already into Marvel would unsubscribe, and they wouldn't attract a new audience because people already have this idea of what they think it is, regardless of whatever Disney could have changed. It'd be suicide for the product if the parent company made sweeping changes to how it operates.
Facebook could turn the Oculus Rift into a social media tool, but what would they gain out of it? There's very little potential. The way I see it, Facebook is simply making an investment with this purchase. They're hoping that it will take off spectacularly, and they'll easily make their money back when the value skyrockets (not going into how likely I think this is).
That said, if Facebook illogically makes the big sweeping changes that everyone is predicting, I'll happily eat my own words. As it stands though, I can't see it happening.