Must a site or community have a bigger problem at its outset? My gut feeling is that the answer is no, that communities become their own thing, and that they can support and enrich themselves in unique ways.
> ...there is also the inescapable fact that at some point men and women will have to work together in engineering environments, and we still have a dearth of environments that foster those interactions.
I don't believe that something like Leap is counterproductive here, but, lacking a suitable algebra of online communities, that's another gut feeling. The Hacker News community is very interested in fostering those interactions, for example.