I avoid posting anything on facebook, myspace, reverbnation (or anywhere else where I promote my band) during the hours when I'm at work.
I never directly or indirectly mention the company I work for, or the people I work with, on facebook, or anything that I've done, said or had said/done to me, while at work.
I have never posted my bank details or my home address or home phone number on any of these sites. Common sense really.
I use Facebook/Myspace/Reverbnation almost entirely for promoting my band. And finding out what my friends are up to. spooky that, innit?