Me and my girlfriend have talked about the fantasy a lot. They anonymity factor is a huge turn on... and it really emphasizes that the cock sucker is there only to service cock .... no intimacy, no foreplay.. just a cock waiting to be sucked. It is very naughty!!
We both want to do it (I'm bi) but would only do it in a more controlled environment, so we'll be putting one in the basement soon for some naughty, role playing fun!