People have webcams in their face many hours a day. On their phones, their tablets, and their laptops. If you're looking out the window, that's not useless - that's data. You are apparently uninterested in whatever is onscreen. Facebook could require your webcam to record when you visit their website, or require your phone and tablet to track your eyes when you use their apps. Undoubtedly somebody at Facebook already looked into it. But they aren't tracking your eyes. It's not happening. Why would the rift be different?
Good point, but at the same time: "social networking/communication" is a far broader scope than "nefarious eye tracking". Yet everybody suddenly seems to define it as solely the latter.
VR is different because it (potentially) offers the user something compelling that they will sacrifice their privacy to obtain. Oculus is different b/c at this time, no competitor has the level of realism they have obtained, and will patent various parts of their tech to ensure they have a competitive edge. And Facebook is different because they are totally 100% based on collecting personal data.
As far as I know, I'm the only one speculating that eye tracking will become a norm in such technology, although some have said the same thing about head tracking. As I said, it seems like an obvious progression to me: head tracking + eye tracking and full body tracking are all components that will become part of VR. In general, people are concerned that FB would collect data for their social network and become a communications giant with the tech they are acquiring and use that for targeted marketing, and there is less discussion about exactly how they may obtain that data or specifically use it. So, I am stretching things to what I think is the worst case scenario, but I think that's important because if you don't look ahead, you'll look back and wonder why you didn't see it coming.