I think this is one of the major reasons why I don't use anything like facebook.
In real life (or at least for most people) judgments are on a day to day basis on how we act. Unless you intentionally mix work with family (like a company pick nick) what you say at work about your family wont make it to the ears of your family (you'd have to be real low or foolish to be like that about it but it's just an example).
For the first few years of the Internet, everyone was anonymous until places like facebook came along, a place on the internet where you were no longer anonymous. Even if it's only people you choose to see your posts or what others have posted about you, it's still a potential cesspool where all our dirty crap eventually comes to the surface (if your like the examples of goof ups this article listed).
I found it much easier to just not participate then it would be to either lie to people and say I don't have one because I don't want them reading the posts, or to tell everyone I have a facebook account and eventually have someone from this site post something that could out me to all of my friends, family and co-workers (accidentally of course).
It might take a little extra time, but I would rather keep each group separate. The people I talk to here don't know my World of Warcraft characters names and vice versa. I don't mind saying I play World of Warcraft to this group, but I wouldn't ever think of telling my World of Warcraft friends I converse on the subject of GID and wishing I was a female at
Susans.org (unless it was a group of people from this forums that wanted to create characters on a select realm and so forth).
On the flip side of this though, real life social networks could prove to be just as damaging as a site like facebook. My SO knows about my GID, and if she ever wanted to be vindictive towards me she could tell everyone on in my guild that I wished I was a female, including my brother who's in the guild (and if she knew I had an account here tell them my screen name here).