After havin' viewed the above posts, an' ponderin', I think it appears as if most us make a cognitive "choice" not to treat others, in our relationships, the way we ourselves do not want to be treated. (Seems like good practice to me)
Though we all seem to have different views about the appropriate lines of 'loyalty' in datin', we all seem to agree that betrayal, in the form of adultry, in a marrital relationship is decidedly unacceptable, perhaps even unforgiveable.
God, Himself knows how to forgive such betrayal, but I know no one on Earth who would do the same, an' I doubt that I myself would truely be willin' to choose to completely 'trust' again if I was the victim of such an offense.
Perhaps that's why folk fear men more than the God who makes men, the fact God forgives an' people don't, seems to create a very definate sense of 'accountability' amoung fellow humans, for most of us, I guess.
Perhaps its best to walk accordin' to the words, "treat others as ya wanna be treated".

(works for me)