It is not what you post, it is what they post about you.

A friend of mine decided to give facebook a try and he was received with a warm welcome of "Bring the cocaine, snuffy is here finally!"

Closer to home, a cousin went to a bachelorette party and posted pictures of her and everybody doing their stuff, you know, sucking fake cocks and stuff. Totally inappropriate for the world to know, but they thought that was just funny.

See? you can't control what they post about you.