One [great step][1] 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.


  [1]: http://blog.stackoverflow.com/2011/08/facebook-stackoverflow/