I'm on the outs on a 14 year marriage, I had wondered if I would cheat if given the chance. Well, about 4 years in I was propositioned by a beautiful (slutty, obviously) Russian girl that I worked with. She made it clear there would be no strings attached. I told my wife about it so that I made sure I wouldn't take the bait.
I ended the marriage because it got to the point where I'm pretty sure I'd be unfaithful if the situation was right.