I've been thinking a lot about what a friend pointed out - that mixed gendered spaces often quickly become male-exclusive because men tend to have much higher tolerance for arsehole behaviour than women, so it only takes one dodgy person to destroy a community as all the women basically leave. Once such a community has heavy male bias it can hardly recover, and its lack of representation means it can hardly succeed in any social, cultural or technical aims. Rings true for the extraordinarily bad gender balance in free/open source software in the context of the Stallman report.