It might simply mean that women enjoy a comparative advantage
http://www.econlib.org/library/Topics/Details/comparativeadv...
at doing something else, whatever the something else is, and they are happy to live in a world in which they trade their ability to do what they do to enjoy the benefits of modern computer technology developed mostly by males.
Philip Greenspun's comments on women in science
http://philip.greenspun.com/careers/women-in-science
may not be completely apropos, because programming as a career isn't exactly the same as research science as a career, but those comments illustrate that simple guesses about what the problem is just might be mistaken.
There's a woman I work with who was a programmer for years, but now works as a technical writer because she was tired of dealing with the cultural problems she had at multiple companies. I've worked with other women programmers who had to deal with bullshit that I'd never accept due to my white male privilege.
There is another option: programming hasn't done a good job of appealing to women. It's entirely possible that it's not a case of women being shut out, but rather they haven't been sold on the profession to begin with. In short: an image problem.
I know this doesn't apply to the situation we have here with this ruby presentation full of porn, but as long as we are generalizing this specific instance into the "why aren't there more women in CS?" question, I thought I'd throw it out there.
It's not like programming is the only profession with this problem. As a male, I haven't been particularly sold on being a nurse either, despite the fact that (in my area) it pays roughly the same and the few male nurses I know love the flexibility to move around the country almost at will. I just never considered it for a career because of the gender bias regarding that profession held by society, not by the members of the profession itself.
But like DHH, I don't think it's anything to do with male programmers. They act no worse than men in other fields, maybe better.
And I don't think this problem is programming specific. It also happens in math, physics, and a variety of other fields.
So, where is this bias coming from? Who teaches girls to take up girly interests? I think it's primarily their mother.
This ought to change. http://www.takingchildrenseriously.com/