This is an interesting question, and as a girl geek who is applying to y combinator and has worked for many startups, I can mention a few things.
1) Startup culture appears to be a boys' club.
a) Have you ever noticed that when you hire the first woman in any company, the dynamic changes? There's resistance to that change, whether it's for better or worse. (pun intended) There's a big sign on your clubhouse that says [GIRLZ KEEP OUT!] Sometimes it's very subtle. Sometimes overt. How many of you actually had women on the short list of people you were choosing to partner with? Some geeky guys still have a hard time talking with girls. It may be an issue with whom you're comfortable sharing your great idea. From what I've read in these posts, you have some assumptions that you're making about girls. Truth is, when you get to a certain level of skill or creativity, assumptions need to fly out the window - for both men and women.
b) With that being said, I love it when work consumes me with a passion and takes all of my time to the exclusion of all else. I have mad skills in a bunch of different areas and startups seem to want me. . . but they don't think of me as a co-founder. I code, design, do market research, marketing strategy, media buys, infrastructure, pitches. . . basically I've worked for many startups doing everything necessary to get started. Still thought of as an accessory - never fully included. My solution to this has been to position myself differently - and I can do that now. I need to market my skills differently from the way guys do. This has been successful.
2) We're not as sensitive to hierarchies and heirarchies' flip side, competition, as guys are.
a) We often just want to get it done. We don't care as much if it strokes our ego or your ego. It needs to be done. If, every time we have a conversation, it becomes a zero sum game of who wins the dominance, it's stupid.
If there's a list of things that need to get done on the table, and some tasks are seen as too onerous for guys' job descriptions (egos), we wind up doing it because it needs to get done. Because we did it, somehow our status falls. We wind up getting stuck with _all_ the crappy jobs, and it winds up sucking for us as our status continually sinks.
b) We assess ourselves and our skills differently. Here's an illustrative example. A female engineer once told me why she gave up working in industry. She was the only woman working with a team of guys. The team lead would throw out a task for discussion on the table. Everyone but she would say they could do it easily. She would say that no, this has these challenges and would take much longer. One of the guys who said that it was easy would get the project and then go to her for help doing the problematic tasks. Who got promoted? The guy. Who was doing all the hard work? She was. Female examiners at the patent office tell the same story. There are a lot of women engineers who leave industry because they can assess themselves and the problems accurately and this isn't valued. Managers want their problems solved. They value gung-ho over truth.
c) This is often linguistic. Men and women use different syntax to express the same thoughts. I need to remap what makes sense to me onto another linguistic pattern and that seems to be a waste of energy. In fact, this has a lot of benefit because it makes us better communicators all around. It's a learning curve - and it's often hard to recognize that it's there or needed. (I was a linguistics geek in college, where I found out that 85% of all conversational interruptions occur men on women, so it's a challenge for us to get a complete paragraph size thought into a conversation - much less complete a sentence without being completely stepped on.)
But even in the more egalitarian parts of the States, there are different linguistic patterns for men and women. If you go to the South, it's much more amplified. If a woman makes a statement with the same intonation and wording as a guy, the conversation just stops for a hot minute while everyone in the room processes it. In places like Alabama, I need to preprocess so that the communication is seamless and the conversational stoppages don't occur - and this often means using what would be considered subservient speech, like ending a statement with a questionmark. Up north, if I'm in a roomful of guys, or even just talking with one, the preprocessing still needs to happen.
d) It may be that because we're not as sensitive to hierarchies and have different sensibilities about status, money means something fundamentally different to us.
e) When I was in college, I really wanted to go into physics, and I was good at it. I spent a summer working for NASA and saw how cutthroat the competition was among the physics geeks and didn't like it. Several years later, I was the webmaster for a hearing research center at a big university. It was a collection of twenty or so labs. I noticed that there were a lot of female scientists, that there was a lot of collaboration between scientists in this particular center and also around the world. I decided to find out what was so different and spent about a year asking people how it came about.
The story is interesting. It wasn't by accident. It turns out that at MIT thirty years ago, there was a hearing research professor who got all of his grad students together and told them that their careers didn't have to be all sniping and competitive - that they could do something different and agree to cooperate. These grad students are now the heads of their own departments. They teach their undergrad and grad students what behavior is acceptable and are growing a culture of deep respect and cooperation. It has a lot of benefits for hearing research as a whole. Work isn't hidden from each other and duplicated - meaning money and time isn't wasted - so it's much better for the hearing research discipline. There isn't the attitude of hoarding ideas for credit. Everyone's resumé has long lists of collaborations. Mostly, everyone's really happy and nice. Apparently, vision research is the exact polar opposite.
I know that in a free market society, competition is seen as creating efficiency, but in a lot of ways, it's very wasteful because of hoarding of ideas and duplication of effort. For people who don't have access to resources, cooperation results in significantly greater value. There isn't nearly as much money available for hearing research, but these researchers are incredibly efficient because they eliminated the competition from the discipline. They're still evaluated. They still have to do their work and be very good at it. It's just that the element of fear is gone.
Alpha males and alpha females see competition differently. How many alpha males can be in a company at any one time? Those who aren't the tiny percent of you who are alpha males feel fear when there's excessive competition. Do you want to work in a fearful environment?
3) If we're single and cute, the dominant chimp will hit on us unless he has a well developed sense of morals. I've been around and around with this one with other women about what to do in response to this and have seen a lot of different strategies to handle it. Some women just shut down their levels of expression and passion for their work. (sucky solution) I know one woman who pretended she was a lesbian. (sucky solution, but one of the most successful - she still retained respect) This comes up a lot at female executive dinners. It's tiresome because when the dominant chimp's ego's bruised there's _always_ retaliation of some form.
4) It may be that y combinator and the VC game doesn't get us where we want to be.
a) If the majority of all small businesses in the States are being started by women, and if we're especially good at communication and customer service, which you'd think would be great for Web 2.0, then what is it about the whole VC game that doesn't get us there? How are we starting our businesses without you? When we're starting businesses, what's the structure like? What kinds of businesses are they?
b) I know that usually VCs or angels don't even look at people until they've spent $50k of their own money. Women have a harder time coming up with funds like that. We still don't have wage parity. We're taking care of our parents or our sister's kids. It's harder for us to get out of family obligations. In the family, daughters are still thought of differently. While I was still an undergrad, I was a founder in a startup. I had to leave to take care of my sick mother. When I asked her if I were a guy, would she have asked me to give up my business, she replied, "no." without any hesitation. We're still expected to do the bulk of non-market labor in this culture. If we say no, there are repercussions. Being a good girl is always for someone else's convenience.
c) It may be a timing thing. Women may have different goals immediately after college. It would be interesting to check to see how old the women are who are starting businesses in this country. I'd want to check the distribution graph - don't just look at the mean or median ages of when they're starting businesses - I bet there are several humps on it - each would tell a different story about that group's lives. By excluding women who are above a certain age, you're cutting out a lot of experience and wisdom. One of the coolest businesses was started by Mary Kay. However cheezy her pink Caddies are, she had a lot of insight into how women ran their lives and built her cosmetics distribution model on those insights.
d) I'm willing to bet that women are starting businesses with less, are entering businesses with lower barriers to entry in general, and that the geeky women aren't starting businesses or aren't going your route to do it. If you look at the percentage of female college grads in engineering and the sciences, it's a much higher percentage than who are applying to y combinator. How are their opportunities and thoughts different? Perhaps you should ask them. You're missing a lot of talent by not addressing it. Are there qualities that you are rewarding that talented women find reprehensible or icky?
By definition, you're looking for special people. The next Teslas are going to be odd no matter where they're from or what their gender is. What would have happened to Tesla if there had been no viciousness of Edison's smear campaigns? Clearly the world lost out. (I have a thing for Tesla, and in an ideal world, Firefly would still be on the air.)
If the next Tesla is currently wearing a burka in Afghanistan, she, and the world, are out of luck. If she's in school just down the river, or has just sent her kids off to college, you may be able to do something about it if you want to.
Am currently doing the bulk of the market research, b-plan dev and giving guidance to the other two in the company who have never been part of a startup. Soon, I'll be doing the visual design and some custom PHP coding and all of the marketing. So much to do! So little time!