The problem with this interpretation is that valid contracts depend, among other things, on informed consent and on the legality of what's being required, meaning you can't trick someone into being bound to terms they never really accepted or sufficiently understood and you can't bind them to illegal terms.

In this case, most people haven't read the Facebook terms of service and it is probably unreasonable to expect everyone to not only read them, but to keep abreast of any updates. So it's a grey area. And if you pass laws and regulations around data privacy, then FB won't be able to legally impose such conditions. But as I said earlier, there isn't much inertia behind data privacy. Nobody with power wants it.