Oh Coolman, you so need to move on. The fact that your wife would suggest this - or even tolerate it, if it was your idea - means that you have NO value, ZILCH value, NADA value in her eyes (Although she may intend on using you as a backup or a source of funds. See Goodoer's post #9 above). Do not listen any of this "Win her back" malarky you are hearing from the Mommie's boys on this board. No woman ever "comes back" to a man unless either:
(1) She figures she can do no better (Do you want to be that guy?) or:
(2) She has figured out a way to make use of a man without crimping her own style (Do you want to be THAT guy?) As has been suggested above: Find a new woman and start fresh. And yes, to answer the original question, I have lived in an open relationship, and also in a West Coast commune where everybody fucked everyone else's girlfriend. We thought this was O.K. at the time. (Well, it's not. Not so much....) Move on.