Sorry I'm late to this party but here's my $0.02:
In the question of Nature vs Nurture, I believe it is a little of both. I believe that there are people who are genetically susceptable to being homosexual, and it takes a stressor in the environment to shift them in that direction. I base my theory on the many friends I have who are gay.
Chip, who is 32 years old and gay has a total shit bag for a mother. his older sister could do no wrong and Chip can do no right. Chip is a very talented artist, designer, and is highly sought after in his job. He and I have collaborated on some really fine projects. he's a generally nice guy. His mom is a beast from hell.
Jamie who I think is about 30, is a lesbian friend who I met via my daughter. She's funny, vibrant and being in her company is always good for one's soul. Her brother, whom she grew up admiring was tragically killed while she watched. I don't know the details, because she can't speak of it still after all these years.
Jon, a gay friend who only recently came out, has always been a troubled soul. i have known him for many years. We were among a group of good friends who drank a whole lot of alchohol in our days. he's adopted and his rich parents are psycho. I never liked them.
Phil, another Gay friend who recently came out, though it was no surprise to anyone, has a past he won't talk about at all. Since he came out he's been likethe phoenix rising from the ashes. The change in him is astounding. He is now on to greater things.
I vote both nature and nurture.