Speaking as a married woman, how exactly did you realize that there weren't others on the site? What did you see or not see that would have been different?

My impression is that many women in online communities avoid visibly female names (because they'd rather dodge the entailed social complexities) and then announce demographic status only when it is topical. When I chose my login name I was aiming to contribute to a sense of real humans with real names taking responsibility for their ideas. Making my gender salient to some readers with every post was a by-product I'd have marginally preferred to avoid. I could have pushed even deeper into demographically transparent naming with something like "MrsRM", but... um... no. That would push my feminism buttons a little much :-P

Given that I'm already unusual in using my real first name online, it wouldn't surprise me if other demographic stuff that I'm not broadcasting was shared by other members of the community. If I was being less transparent and considered myself typical then I'd be more likely to think that "people like me" were common here, simply because the predicted paucity of evidence would leave my expectations closer to the base rate :-)

For what its worth, the recent (first ever) San Diego meetup had a relatively good mix age and gender wise: about one third female, at least one undergrad, several people old enough to have adult children, and some in the middle. It was the first meetup and maybe we'll end up with evaporative cooling on relatively arbitrary demographic traits, but I hope we don't.

Speaking as a single guy, vacuuming is one of those things one is never done with.