Well, let's put it this way: "The market can stay irrational longer than you can stay solvent."
You can stay away from Facebook and then feel really smug ten years from now when it eventually collapses. But until then, you'd have missed out on a lot of important things. The only winning move is to realize that you do not have a choice, and that the terms of service are just an illusion.
For the record, I think Facebook's existence is regrettable. But the notion that you have any ability, choice, freedom, right, or opportunity to opt out from it is laughable.
As for the idea of the social contract, I think you are actually spot on:
> Social contract arguments typically posit that individuals have consented, either explicitly or tacitly, to surrender some of their freedoms and submit to the authority [...] in exchange for protection of their remaining rights or maintenance of the social order.
Individuals have:
[?] consented explicitly
[x] consented tacitly
[x] to surrender some of their freedoms
[x] to submit to the authority [Facebook]
[ ] in exchange for protection of their remaining rights
[x] in exchange for maintenance of the social order
In fact, it could even be argued that this de-facto state of affair ought to be made de-jure. Certainly, it is the case already today that many of my local government agencies are more active on Twitter or Facebook than they are over phone or e-mail. In fact, they rarely use e-mail for regulatory reasons. If someone is suicidal, has an extreme drinking problem, or holds extremist political beliefs, we consider this a transgression and rightfully lock them up/commit them to involuntary psychiatric care. Why is this not the case for all self-harmful behaviors?
Considering many employers etc. already want it, it doesn't seem far-fetched to consider people hermits for refusing to participate, just as we consider an individual defect for not owning a smartphone.
https://www.youtube.com/watch?v=lMChO0qNbkY