There is an accelerating flood of niche social news sites; it seems more likely to me that in a few years there will be a huge number of these kind of sites (and many platforms to let you make your own), which in aggregate will probably follow a power-law distribution of user populations.

Recommendations is a good idea (never figured out why it doesn't work at reddit), but only for the 'fat head' of the curve, for the long tail the problem almost takes care of itself. Also, better categorisation would be useful, and would help with recommendations too.