no offence guys, but to say that it is purely social conditioning is a difficult case to make when you start looking at the studies that have been done on it, and to my mind it can be very easy to say well "they were brought up in an enviroment that turned them gay" without fuly assessing what a "gay" enviroment is.
There are still people who argue for social factors as being the key cause of it, but the evidence, to my mind at least, weighs up quite heavily in favour of biological explanations. Note that when I say biological I'm not saying genetic, things can be biological and environmental at the same time.
Here's two wikipeida articles on the subject, one arguing for environmental factors, one biological (although, the enviromental one should be labelled as social...)
http://en.wikipedia.org/wiki/Biology...al_orientation
http://en.wikipedia.org/wiki/Environ...al_orientation