there are two directions in which privacy has to work right.
1.) privacy "against" all other users of the fb-plattform
2.) privacy "against" the coorperation that runs fb (and of cause it's partner's)
until now i were not able to find privacy sitting for "2.)"
it's like with everything:
something new == everybody shifts towards it
after a certain amount of time == it levels itself out and heads back to where the use influences the outcome in a natural way
wait... someone stole my segway... no problem, i let my new iPhone-App "Find my segway, and do evil things to the thief" handle it.
But if his wife then see's that the überpoison she placed in his dinner has no effect on him, she well might think that he's the (... checking wikipedia for the correct spelling...) Kwisatz Haderach.
Imagining what that would mean for us all... to you i leave.