Facebook has always been bad at building communities outside of your existing friends and family. It’s an online tool to build and maintain your existing community of relations.
In fact, social networks in general have been bad at bringing together people with a shared interest to create new communities. Whereas forums have always been particularly good at it. Look at Mumsnet, The Student Room and Gamespot for some incredibly successful examples of forums used to build powerful, long-lasting communities.
Read more on Emerging niche social networks and the bond of community…