I read an interesting article that says according to a new study, 20% of long term relationships begin when one or both partneres are involved with others. This is called "mate poaching." People left previous relationships to be with their current S.O. and some were lured away from their current partners by current S.O. (Psychology Today, June 2004)

Have any of you lured your current S.O. or left an S.O. for another person? So you didn't exactly cheat on them because you didn't do anything until after you left, but you left for this new person.