Facebook is lots of people putting on a charade. I've played, too. You put on a fake persona that is your maximally awesome self. Every like, share, or comment, is done with calculated forethought and with the result in mind. How will people interpret this? Will it project the right image of me? Will my net opinion be increased or decreased among my Facebook friends' by this action? Is it compatible with current and/or future employers?

Of course, there are probably people who don't care what other people think about them on Facebook and are just totally open. But I don't know any of those people.