The world of niche social networks capitalises on the awareness Facebook brought to general public. Everyone knows how to use a social community site now. Moreover, (just about) everyone has a Facebook profile and Dolphin helps to take advantage of Facebook API to draw people to your site and make them feel comfortable! Dolphin Facebook login and extensions can help you go as far as building a full Facebook-clone and templates can make your site look like Facebook, but there's a lot more to it...
Check out Facebook comments integrations, inviters, friend suggestions, integrated Likes, notes and even alternative Facebook Connect plugins. No need to de-throne the big blue giant - use it to grow your own social network!