I see it on the boards here a lot. Women interested in men who already have girlfriends or married men. Why go after a man that's already involved with someone else?
Is it the challenge? The fact that he must be a good man because someone else wants/has him? Do they not care? Do they have no moral standards? Do they like being homewreckers? Do they have little faith in the single, unattached men?
What is the attraction?