Apparently dating can be a good strategy to help the WAS realize what they're losing. So I guess it could be seen as doing what works.
I could see people doing it when the situation has been going on for a while, one or the both of you have filed for divorce, and you're ready to move on.
I'll admit I have religious/moral beliefs that prevent me from doing that. Plus, I always think what kind of person would date a married man or woman? Plus, I have 2 kids and I like at least one of us to be a good role model for the kids. But I really do think it has to be a personal choice for each person as to what's right for you.