Interesting article, to say the least, although lacking on the scientific end of the equation to be sure. I'd certainly be curious to know how well any of this "scientific research" held up away from the metropolitan centers of the country.
I think my opinion can be summed up by a couple of sentences from the article itself: "Gaydar can no more be proved than a sixth sense... What’s being classified as fundamentally gay is nothing more than cultural signals that vary so much from one part of the world to another that they’re worthless as clues to anything."
As for the biological aspect, there are definitely genetic variables involved...it's a hallmark of any genotypic or phenotypic characteristic. That said, I believe there are also nurture aspects working in tandem with those from nature, even if they only influence the comfort, if not the direction, of orientation.