A lot has been said about promiscuity and the impulsive nature of people, but I have a question?
For men, if a woman told you "Fine go out and have sex with anyone you want." If you are a man that likes "Forbidden Fruit" and doing something because it is wrong, does this take away the impetus to sleep around, or only make it acceptable?
I am sure some people do it because cheating is taboo.
It'd serve as an excuse to do it. While some may be willing to do it anyway, saying something like that gives easy leverage for the discussion after it happens.
It's the difference between "How could you!?" And "I didn't actually mean you should!" (if not just being weak and just accepting it). Very different paths of discussion that can end on different notes.
I know in my own case, if someone gave me such an okay, I'd figure either:
A) Relationship has problems and will more than likely not last from here.
B) Comment from heat of the moment, being flustered, etc.
C) Person's trying to absolve themselves of their own guilt for having cheated first.
In that sense, it would make it a good deal easier to do so than otherwise.
So, why's the question only for men? In my lifetime I've actually seen more women cheat than men. 
LOL!
No... That's like asking if you set a six year old loose in a candy store and tell them they can have whatever they want that they won't eat anything...
As someone who's been in multiple open relationships, and actually had multiple women living with me at one point, I can assure you, that the only thing that will make the concept of forbidden fruit go away is having to deal with multiple women bitching at you for attention after the fun part dies down... Dealing with the emotional needs of one woman is more than enough work for any man, having to deal with 2 women nagging together... will drive you insane.... It's totally not worth the trouble...
But yeah, if you tell your dude to go out and have fun... he will be hesitant because obviously that's a trap (in the minds of most men) but with enough reassurance he will do it... It can in many ways increase your bond through a deeper sense of trust. But the obvious worry is that he will generate emotions for someone else and potentially split you away from him.
Either way, you're playing with fire kitten... and someone will burn for it... I'm not saying it can't be fun... but it will be dramatic...
"Dealing with the emotional needs of one woman is more than enough work for any man"
It's really not that bad. I've found by paying attention I can usually circumvent the nagging by finishing their thoughts for them. Once they think you're in their head, or that you listen too closely, people tend to nag less. Every word is ammunition, and that, at least for me, made it stop being horrible and become fun.
"he will be hesitant because obviously that's a trap (in the minds of most men) but with enough reassurance he will do it... It can in many ways increase your bond through a deeper sense of trust."
A relationship that's rife with tests of trust suggests that there are reasons for it not to be there in the first place, or it shows heavy levels of insecurity. Such games would serve to push someone like me away, not bring me closer, and I suspect that to be the case for many others. It's a rather disgusting form of weakness on their part to "grant" freedoms they don't themselves have conviction behind.
Mid-Twenties, I'm still fairly young. I'd probably have had more relationships if not for said ex who isn't speaking with me anymore (due to us being childhood on-again off-again's for dating, plus an engagement that fell apart), but that also means I could have had a lot more rejections or short term flings too.