I think with most straight men (and much of what I see being said by the virulently anti-gay folk upholds this thought) the portion of sexual activity that defines something as 'gay' or 'homosexual' more than anything is the act of penetration. In heterosexual intercourse the male penetrates the female, never vice-versa (not with a living penis anyway) and so being penetrated is too uncomfortably a feminine position for them.
You might be on to something there.
I've known a couple of rabidly straight guys, so straight that they swore they'd actually do violence to any guy who so much as flirted with them. That never made much sense to me: I'm a woman, and guys flirt with me all the time, and if I'm not interested the response is simple (and doesn't involve beating the living daylights out of anyone).
I've made it a point to ask such men what they're afraid of, what bothers them about being hit on or flirted with by other men. None of them really have an answer - it's like they don't actually know what bothers them about it. Until I ask them: Are you afraid of being raped?
And then they tend to get really, really quiet.
Which makes me wonder: are hypermasculine, anti-gay males afraid of being raped? Is that part of the revulsion about all things gay, that an openly gay male is too much of a reminder that men can penetrate - and perhaps violate - other men sexually?
Makes ya wonder...
Veering back towards the OP, I'd guess there's probably a lot more sexual experimentation going on than not, and I'd see straight men "trying out" gay sexual encounters as part of experimenting. Plus I don't think that sexuality is black and white, either, I think it runs along a very gray spectrum, and most folks are probably more bisexual than they're willing to admit.
Levi501, let me be an exception to the rule you've found, about women not wanting to date a guy who's experimented with other guys: I have no problem with it at all. Indeed, I've been in long-term relationships with guys who had experimented with other guys.
But then, I'm a little weird that way, and like to refrain from judging people on their sexual history.