Cheating!!!
I believe that if you're in a relationship with a person then it should only be that person. I can't see myself forgiving a guy that cheats on me because if he does it once then he's going to do it again.
If we succumb to the belief that all men cheat then we're only going to end up making it true. Not all men cheat and if a man truly loves you then he'll control himself. Cheating shouldn't be something that women should expect in a relationship, no, the more we do that the more we actually encourage it in a relationship.
If any guy I was dating ever cheated on me then regardless of how much I love him, I'd pack my things and leave. Relationships are sacred, their like mini marriages and if you can't commit to me when we're dating then you sure as hell won't commit to me when we are married.