The Open Source movement, by contrast, has built up from existing partnerships (largely from the Real World) forming relaxed coding collaborations. The larger projects have then acquired others from across the net who were interested and got involved. The key here is that OSS is a community responding to a collective demand.
So how about filling in that great Venn overlap of community drawn by solutions to individual problems, and the productivity of a community solving a larger problem together? In other words, SO, give us a collaboration hub. Surely it's the ideal place for the inexperienced to participate at the fringes of an OSS project, and for experienced coders to progress up the kudos chain by contributing work and experience to a project, rather than a single point of expertise.
The system, interface, ranking, discovery and how it all overlaps with the overflowing stack of questions and answers on SO are subsidiary issues. But since people's individual project gave rise to problems, which gave rise to the need for SO, let the circle complete, and the solvers coagulate and combine to produce new projects.
I came, I saw, I solved, I wondered about the project, I got involved, we collaborated, we solved, we progressed, we share the story, we conquer.