I really don't think being gay is anything that can be determined by genetics. Or if it [i]is[/i], I highly doubt there is a single, isolated gay gene. Like height, I would assume it's affected by a range of other genes.

Anyway, I guess it's the same as asking why some people like the color green and why some don't. Why do most people like the opposite gender? Why are most people right-handed? And remember there are bisexual people, as well as asexual or any other sexual denomination.

As for the born with it vs. chose it argument, again, who the hell knows. But I dont find it odd that people could just choose their sexuality. It's like choosing the person you like... If you introduce me to someone, I either feel an attraction or I don't. Sure the feelings can change, but it certainly feels outside of my control. Unless I'm making some kind of unconscious choice. I don't know. But like any of our other preferences, not just the sexual ones I mean, they don't seem to be chosen. 

But wait, if it can't be determined by genetics, and it isn't a choice, then what the hell is it? O__o Environmental factors, maybe? Maybe our genes make us more responsive to environmental factos that turn us gay? What? I just confused myself.

Anyway... I kinda very vaguely remember picking up a pencil in preschool, testing out both hands and just picking my left. That's also what happened with guitar... Actually I play Guitar Hero left-handed but I play the real guitar right-handed. Is sexual orientation that simple? Maybe.

Anyway, DAMN. Sorry for my rambling; I know I haven't made one argument. Just thinking out loud. Whatever. I'll just... er, yeah. *backs out slowly*