So, this is my second attempt at building something people want. How am I doing? ZoooV is a social news site for niche subjects. Here is why I built it:

With the big social news sites: Digg, reddit, and recently after the name change, news.yc, the discussions tend to become more general as the communities grow because we, the readers, have different interests. And because of that, only what's common to everyone goes to the top. Smaller communities have more focus, but it's hard for them to survive because there is less to read, and therefore, we tend to visit them less often and eventually forget about them.

I'm trying to solve this by keeping the communities smaller and focused, but allow the individual reader to choose the communities they like and I create a custom page for them where they only see what they're interested in. This way, even though the individual communities might have low volume of stories, the reader will always find something interesting to read in one of his communities or the other. It's like how an RSS reader allows us to keep track of low volume blogs because we don't have to remember to visit each one of them.