Gay is an identity and world view I developed over time through friendships, shared social spaces and cultural references with other queer men and women. Most of my friends are gay, out to everyone in their lives and seeking romantic partnerships with someone of the same sex.
I am also a total bottom and generally seek out dominant, masculine tops for sex (or they seek me out). This is not a scientific survey since I don't know anything about the anonymous guys, but I'd estimate that about 1/3 are publicly living as straight men. They're not exactly closeted or ashamed of having sex with other men, it's just that they are more comfortable in a hetero social world because of their personality, interests and demeanor. They may or may not have female partners but they're not really interested in dating a man and they only top.
Another third are formerly straight and now bi-identified but mostly having gay sex because they're pigs and it's more convenient. (Crystal may have played in a part in their rapid transformation.) Luckily for me most of them still top most of the time.
The final third are gay men who are top or vers-top and usually more macho than the average gay man and more comfortable around the straight/bi MSM crowd, but still identifiable as gay when they open thier mouths.
I don't think this is a typical breakdown for everyone as it depends on your type and where you live. When I lived in a big city and didn't party, it was 100% gay men. When I began partying and having group sex I started meeting more genuinely straight and bi guys who were horny bastards and openminded to what sex with men could provide. When I moved to a more rural area, I met even more men who had no interest in living a gay life but who were very much interested in pounding the fuck out of my hole. I have to say it was refreshing and I'm having some of the best sex of my life. They don't care that I'm gay, half the time bathhouse hookups ask if I'm married (to a woman), but they do care that I'm a faggot cocksucker who will do filthy things that would make even the town whore blush.