There are too many niche social networks these days. Aside from those you mentioned, you have Subreddits and Stack Exchanges for pretty much everything you cou

There are too many niche social networks these days. Aside from those you mentioned, you have Subreddits and Stack Exchanges for pretty much everything you could form a community around. Actually, I think that's Facebook's problem. It's not a community. It's an interactive contact book. You're expected to add everybody and the conversation turns to mush. As the Roman philosopher Seneca said: "To be everywhere is to be nowhere."