Sqad: Absolutely. As far as I'm aware (though my knowledge of it is about 4/5 years out of date) the scientific investigation into it has thrown up lots of possibilities, but it's very far from conclusive (aside from the ruling out of prevailing hormonal explanations back in the '70s/80s). But the questions they've raised are certainly a lot more compelling than any 'nurture' theorists that I'm aware of have come up with.
Personally, I'm certain I was born gay. I was raised in a loving, stable household, and never thought of my father as absent or my mother as over-bearing (the usual preconditions for psychological explanations). I can't remember ever not feeling attracted to the same sex, and I didn't really know much about homosexuality until after I came out at 17. Hence it kind of gets under my skin when people make assertions about the nature/nurture argument.