A small community space supporting a couple hundred users at the most.

User accounts are owned and controlled by the users by means of a private key. (And thus the same identity or multiple linked identities can work across different "facebooks")

Entire social graph, data store, and all relationships and actions are public-ledgered, fully transparent, and available for download, archiving, and re-homing.

Moderation is also fully transparent, performed by volunteers who are part of the community on a rotating basis, and heavily aided by bayesian filtering.

Hardware and software maintenance costs are covered by voluntary payments and effort investment.

Is there anything I missed?