I searched and did not see that anyone had posted this yet. Rather interesting article, despite my lack of interest in Facebook itself.
The gender gap has the same root causes as a ton of the other ones. Firstly, is the stereotype that only nerds like math, science, technology. I personally grew up from a very early age calling me a "nerd". It was something that I saw as a positive thing. For those who don't see it that way, it can drive them away. Secondly, is the fact that CS is already largely composed of men, and that can, both in stereotype and environment, drive women away. Same reason men will avoid nursing or teaching. You don't want to be explaining to people or to deal with people surprised you are in X field. Also the things mentioned in the interview go into this sort of area. When a group is composed of people like X, and you are a person like Y, it's going to be harder to make friends and get along well. I've heard claims that a lot of it also is that men tend to "tinker" more with computers and such. Men (in my expierence) aren't really pushed at all to be all that social, so spending your whole life playing video games or messing with computers is far more common. Some also claim there is a biological component there (tactile vs social), but I haven't really seen the studies.