It's bad. Don't do it.
No but really, it's so pointless. Why? Do you like get a thrill out of it? Is it fun to watch the other person suffer when they find out? (And they will find out, it is inevitable). If you are not happy in the relationship then get out. If you are happy in the relationship you should not have a reason to cheat. If you are a polygamist then make sure the others in your weird little 3, 4, 5 way relationship are happy, agree with it, and most importantly KNOW that you are a polygamist and don't settle for only one person! Those are my rules, like it or get out.
