One great stepgreat step towards this goal:
Ever since launching, we’ve gotten requests to start dedicated communities for niche programming topics, but we’ve always been hesitant to do so for fear of balkanizing the great community we already have. So we came up with a solution that provides the best of both worlds. We can now create a mini-site by selecting relevant tags (in this case, anything Facebook related) and grouping together just the content from those tags. When you visit a mini-site, you’ll see only the content from those tags. Not only will you be able to see only questions related to Facebook, but the reputation on the user ranking pages will also only show reputation earned on questions tagged Facebook.
The key to this functionality is that you’re seeing a filtered view of Stack Overflow, much like if you set up a favorite tags view. That means that when you ask a question on Facebook.SO, you’re still getting access to the entire community of 750,000+ users, and any questions you answer there count toward your Stack Overflow reputation, too.