Would would piss you off if you found out about it afterwards?
I'm automatically assuming that everyone would be royally breaking up with their partner if cheating was involved, but what else would piss you off?
I find this a really interesting question, as a lot of people I know who seem to be really sensible at all other times seem to suddenly adopt a "well boys be boys ay!" attitude when it comes to stag dos. Yet for hen do's the most outrageous behaviour tends to be limited to penis shaped paraphernalia and weird sashes.
I'm still thinking about it on my side!