No one has ever asked at work...although I'm sure a couple of my office mates wonder. If they ever did ask I would say it was a forum for my professional organization. (And the AMTA really does have one so it's wouldn't be too far fetched)
My friends don't really say much...and since the internet is much faster here in the office I'm rarely on GC at home anymore. My boyfriend lurks around on GC himself...he really can't make fun of me at all