Maybe I'm not being the authentic me when I don't make dirty jokes to my Grandmother that I would to my friends but I'd view that more as simple respect.
People aren't one dimensional, they behave differently in different contexts. Facebook takes away that context. People who would normally only see you in one context (professional, respectful, whatever), may now see you outside of that context, which forces you to act in a way that is acceptable in any context.
