As the internet becomes more generic, (*ahem* Facebook), people are going to start searching for networks where they can connect with a specific audience who is very much like them. Luckily there is a niche for everyone. Whether you are way into knitting, crocodiles, or space, there's a network out there filled with people just like you.
The idea of a niche site isn't new. In fact, forums, blogs, Listservs, message boards, and even Google groups have paved the way for larger sites, like Facebook and Twitter, and have been bringing people with shared interests together for years.