I would say my interest in anal is at least partly fueled by it's taboo status. It's similar to the fascination with oral sex. They were a big turn-on until they started to become more of a regular foreplay, though I guess whether swallowing has lost it's taboo is debatable. If it got to a point where one could walk down a high school hallway and hear common talks of anal sex acts, then I think I"d have to move on to something further out of the mainstream. (Maybe that SM stuff you mentioned?) Just a psychological issue that I can't be the same as the rest. Another part of it, maybe stemming from the taboo idea, is the amount of trust and giving up of control that it involves.