One cam]n never get off completely. Only when you die and someone shows them a death certificate....I have heard. You can log out but they still have all your information.
even worse, after one deletes their page, they tell you can still restore it for 30 days, at which point they delete it.
Thus, they still have all your info, but give those that believe them a false sense of security that info is gone.
It's gone to the public, it's gone from your mind, you breathe a sigh of relief, all the while in back smokey rooms, your info is at the use of black hats.