I vaguely recall a study that tested both males and females against various orientations in pornography. Women showed arousal more consistently at all combinations (male/female, female/female, male/male) regardless of their self-identified orientation than males who (as BoB has suggested) reacted only consistently according to their self-identified orientation. I'd look for a source, but that's probably not the appropriate kind of thing to be researching at work.

Then again, neither is posting on a Final Fantasy message board.

That said, my girlfriend has made out with her sorority sisters in the past "for fun." No particularly sexual motives. It was something that had happened usually for the benefit of an audience rather than the participants.