Although I find this thread entertaining, the quote FROM ME that precipitates it has been misconstrued by Mr. Gin. I certainly do not think sexual orientation is PERSONALLY elected in any significant way. I was referring, in the quote, to the act of choosing to reveal your orientation and thereby inviting an avalanche of stigmas.
That said, I do not subscribe to the idea that a particular sexuality is wholly given with biology. The term "gay" refers to an identity based on homosexuality. That idea -- that the object of one's desire somehow constellates your identity -- is recent in human history.
You can go all over the world and find men having sex with men and not identifying as "gay" or "homosexual." This is especially true in the Mediterranean world, including the Arab world (and we saw how that is getting played out in western terms in the Egyptian court cases this week). This was also true in the ancient world. A system of educational pederasty -- utterly bizarre to our minds -- allowed adult men to penetrate teenaged boys without stigma. But to be penetrated as an adult was taboo. There was nothing called "homosexuality." Sex between men did not constitute an identity and was not incompatible with marriage to women -- who, of course, were just another object of penetration in that time. Sexual stigmas were based on penetration, not on gender relations and women were beneath boys in their sexual status. (Plato rhapsodized boy love.)
The advent of gay "identity" -- as a set of characteristics describing men who only have sex with other men -- is extremely recent. (There is a great book, "Gay New York," Geo. Chauncey, that demonstrates how the Mediterranean ethic regarding sex between men prevailed throughout much of that city early in the last century -- and how "straight" and "gay" cultures blended quite comfortably.) The popular description of "gay" as a fixed and pathological identity began with the American academy's perversion of Freud's theories. (Freud actually had no trouble with queerness.) A diagnosis, of course, becomes an identity. Concomitant with that, a host of legal prohibitions were established, so homosexuality, the identity, also became a crime.
A movement in the late 40s, led by the Mattachine Society, began to resist the legal prohibitions. The movement was dominated by people in the american communist movement, interestingly, and they wanted to conceptualize homosexuality as a social movement opposing the dominant culture. They were booted out by people who wanted to assimilate and, pathetically, actually supported the pathologizing of sex between men but pled for compassion in the legal system.
Then, in the '70s, with the so-called Stonewall Rebellion, a more radical, separatist group prevailed. It was then that homosexuality congealed fully into an identity. One had to come out, to declare oneself. Borrowing the feminist maxim, sexuality became political. This is the still present bind of identity based on sexuality, of course: If you don't purchase the identity you can't have membership in the group...and you need the group for political leverage to gain civil rights. But what happens if you don't like the group mindset?
So, my LOOOOOOOOOOOONG answer to the question is that sexuality is somewhat given, undoubtedly inflected by culture. (Sexuality can be constructed by the culture, apart from biological inevitabilty, and be quite nonelective.) However, the assumption of an IDENTITY based on the gender of your love object is elective in large part.
I straight-identified when I was in my 20s, got married, got divorced and then gave expression to my same-sex impulses. I found queer culture -- an outlaw culture -- very attractive at the time, so I assumed a gay identity. HOwever, I have utterly no doubt that were I given the choice TODAY, I'd not assume that identity because I don't respect what gay culture has become by and large. But the abdication of the identity label doesn't mean one stops the sexual behavior.