You see, I have long held this theory about "gaydar/gadar" -- the presumed ability to spot homosexual men (yeah, I think it's generally used about gay men and not so much about lesbians). It's sometimes a joke and it's sometimes not a joke. And actually, I think that in recent years the concept has much less currency than it used to, now that many more people are aware of the homosexuals in their midst and the super-secret club doesn't require the decoder rings and specialized handshakes of yore to join. Still, the word and the concept are still with us.
My belief is that gadar simply means that the person you are encountering reminds you of gay men you have known. If the only men you've previously met whom you knew to be gay are drag queens and others who display various stereotypical cultural indicators of homosexuality (often confused with cultural indicators of effeminacy, but that's another topic), then your gadar will be of a fairly broad-brush sort. As you get to know more and more gay men you start seeing other things, things that can be quite subtle.
For example, in the Bad Olde Dayes of Secrets and Closets, one of the things that set off gadar was not a flamboyance of manner, but a repression of manner. Men who had an air of self-control, even tight-assedness, reminded you of other gay men you knew whose continuous lifetime efforts to hide or deny their homosexuality resulted in a generally repressed manner. So when you met somebody with a similar manner this little subconscious ping would go off, not so much telling you that this person must be gay but putting you on the alert for other things.
What happened to me over time, because of my social networks and my location (Cambridge Massachusetts) and my job and, eventually, my early Internet activity was that I began to meet more and more gay men who were geeks. High-Tech Gays have been marching in Pride parades for decades now, and I usually know a decent percentage of them in every city in which I've attended a Pride parade. So, of course, I would meet somebody new and they would remind me of various other people I knew who were gay and that little subconscious ping in the back of my mind would send me the message "Oh, this person is gay" and I would have to stop myself and think "No, this person is a geek."
My gadar and geekdar remain hopelessly entangled to this day.
This became vividly apparent to me at the SAGE-AU conference in Perth in September. At the USENIX LISA conferences in the US there is a strong and visible gay presence. People have even complained of the "gay mafia" at USENIX -- which the actual gay mafia responded to by giving ourselves mafia nicknames. (I am "The Bard".) One year I had pink ribbons made up that say "Gay Mafia" which we attached to our badges.
Anyway, I went off to Perth and I met lots of fun folks who, for obvious reasons, reminded me very much of many of my friends I know from the LISA conferences. Except in Australia, they were straight. Well, as I've said, everything is topsy turvy Down Under. But my gadar/geekdar confusion was so evident so quickly that I didn't even try to recalibrate my gadar (as I had to do when I moved to Minnesota) but I simply unplugged the machine.
I have to do the same thing in San Francisco (unplug the gadar completely for the duration of my stay) not because I get so many false positives but because the damn thing won't shut up. (Oh a gay man -- oh a gay man -- oh a gay man - bing, bing, bing). Yikes.