http://vi.to/designers-and-women-in-open-source.html

Basically open source software development (which is a social activity) has about 2% participation by women.

Part of the reason is that negotiating in the open source community can be hostile, the other reason is presented by the webpage linked above.

my favorite quote from that page

here’s no perceived value in open source for mentoring, facilitation, disciplining of unruly users, training of newcomers or non-technical users, etc., which are needed to support both designers of any gender and women in any role