There actually may be a more realistic middle ground that many of us "older'uns" are seeking and that is, WE want to choose to whom we reveal ourselves. It is not necessarily to no one or to everyone, but rather people, institutions, whatever that we choose.
As this thread has pointed out, that type of determination may not be possible with Facebook and its similar ilk.
Except that that hasn't been possible for at least the last forty years or so.
Facebook and the advent of the computer age hasn't actually eroded privacy the way we think it has. What it's done is made it impossible to ignore the fact that our privacy was already eroded.
It started with telephones and credit cards. Credit cards alone give you an incredibly detailed picture of someone's life; put 'em together with phone records and oyu can trace who that person knows, who they're business rivals with, who they're sleeping with, you name it.
Add grocery store discount cards to the mix and it gets even better--and available to more people. Throw cell phones into the mix...well, you get the idea.
Privacy is an illusion. You haven't had it for decades. Facebook didn't make that happen; it just took the illusion away.
