We use camp names at my Girl Scout camp. I've been Indigo ever since I was a WIT, and I respond to it far more than my real name. The kids love to try to guess our real names, and we're not supposed to tell them, but some people do. I sometimes tell a few at the end of the session. Other than that, when the girls pester me, I just tell them, "My name's really Indigo. It's what I call myself, how much more real can you get?"
The reason we were told was that there had been security issues, with campers' parents contacting the staff directly to harass them. That must have been ages ago, though.
