Do you believe in cheating?

[meak]

If it's clearly an open relationship that both parties agree on, why not? If the other person doesn't know, it's a betrayal and just really, really mean.

If it's an open relationship, I wouldn't consider that cheating.

I'm friends with a handful of polyamorous people. They're good fun (without being involved). They have really healthy mindsets.

That's a good point. Okay, all cheating is bad then. A possible exception if they cheated first but then it's questionable if the relationship is already over to have someone to cheat on.