I've been thinking about that a lot and plan to build something I'm more interested in:

• powerless instances where all you can do is create accounts and store stuff to be served but every logic and integrity is done by clients
• anonymous account creation so that everyone can participate -> freedom of speech ...
• follow-based interaction: if I don't follow you, you cannot send me anything -> ... not freedom of reach
• because instances are powerless they do not define community anymore. Communities are good old accounts, created, managed and animated by users directly
• because clients have all the power, they are the primary storage source
• Communities are the primary dissemination vector. If I don't follow you but we're both part of the same community and you post something to that community, I'll see it
• when I block someone, that block can be propagated to others so they can automatically block that same account. This works for communities as well.

Hopefully a design like this should empower users and communities by letting them focus on the social aspect of building the group, nurturing it, instead of the technical parts that constrain users into artificial uses