A decentralized social network should have trust-less servers. The servers should just store encrypted data and serve it up, without being exposed to the social graph and with other metadata minimised.
Identity should also be independent of servers (and hence DNS).
At the networking layer they will also need to use something like onion routing or a mix network to fully protect the social graph.
With that limitation, it would be impossible to replace the centralized services as the UX would be far worse. With modern web apps 100ms makes a difference in loading times.
Identity should also be independent of servers (and hence DNS).
At the networking layer they will also need to use something like onion routing or a mix network to fully protect the social graph.