I thought I'd just put some sort of twist to this whole "secret number six" bit - men have a sort of lock-on device to women. It's built somewhere in the deep little crevices of their brains to find a woman and procreate, as pure instinct (since humans are animals with more aggressive males than females when it comes to spawning the species, scientifically speaking). Now, I can't exactly explain gay men, but I can explain this easy-for-girls-to-turn-bisexual thing: women don't have that lock-on. They don't say deep deep deep in the back of their brain, "MAN. SEX. BABIES." Soooo, technically speaking, all women can be bisexual, but straight women and lesbians are just picky. Me, I'm bisexual 'cause hey, why cut out half the human race just 'cause you can't have babies with them? *shrug* As long as he/she's hot, I'd hit that.

I dunno if this comment applies to what you were thinking of, but I just thought I'd shed a little more light on it.