Buttons840

I've thought of creating a social network that groups people into small groups of 100 or so, by interests and location. I would advertise it as a chance to escape the monoculture and explain that the cost if you must participate a minimum amount, like 1 post or comment per week on average or something. And then you could mix up the groups every year or two. It would have its pros and cons, but it would achieve the goal of letting small groups form and create their own cultures. It would also succeed regardless of its size, so long as you have enough users to form a small group.

capableweb
You're effectively describing Scuttlebutt in a nutshell. Small communities that are formed ad-hoc by peering with each other. "Follow" mean you'll help replicate their content for others who follow them + you. Scuttlebutt is already successful even though it's very small so far. Tags and other things can be used to explore content on the network, as long as you've found an entry-point.

I'm a bit split about spreading the word about Scuttlebutt, I don't want to ruin it since it's already so great. But felt it was very related to what you were writing, so here goes nothing :)

In case you wanna join: https://scuttlebutt.nz/

The client I'm using is https://github.com/ssbc/patchwork