I never understood the concept of fucking someone who is already taken, pussy isn't worth ruining the lives of others over. Might even be your own, if said jealous husband has a gun collection and a penchant for buggery. Buggery being shooting people in the face that is.
Friend of mine nailed my roommate's girlfriend, repeatedly, which fucked up 10 other people's surroundings and things were never the same since. What was the point? Apparently she was a lousy lay anyhow. Well, that dude is specifically attracted to female's of the forbidden variety, which is just another can of worms, but still.