I've never read this thread before...
I think any woman would cheat on a boyfriend/husband given the right circumstances.
It's funny how often this is said, because most people would do things a lot worse in certain circumstances. Like in Nazi Germany or in psychological experiments for instance. Its asking a lot to expect otherwise. Though, there are women out there who would need some real extenuating circumstances to do so. Just as there were women out there who risked their lives to save Jewish children during the holocaust or died for some other cause or other.
Morality today roughly as I see it:
The goal of sex is to reproduce and in ideal or stable circumstances for you to go on to be a good parent afterwards. Pleasure, is a means of making that goal a 'goal' for you. And this goal is often called moral.
However, we don't always live in ideal circumstances. So, we have a degree of flexibility in us. In times of anarchy for example, it may have been most important that we were simply able to reproduce at all, perhaps due to morality rates, or conflicts etc. So, the ideal, the moral, while it is still the healthiest path to take where possible, is not fixed.
Now consider this. How much of today's music, films, television, nightclubs!, news etc. is designed to put us into some kind of a fight or flight response? I think just living in, even a relatively peaceful urban environment is unnatural enough, with large, deadly vehicles flying around us all the time, when we can see and are surrounded by more strangers in a day then our ancestors would have seen in a lifetime. Philosophers have been banging on about it over two hundred years now and they thought it was a serious situation then.
Just imagine what all this does to our view of the good 'goal'?