Decentralization in the context of social interaction services does not work. As long as the concept of a social network exist, people will connect to similar platforms.

It's been tried, again, and again, and again, and it fails for the same reason all such projects fail - the only people who care about this architecture stuff are those who are geeky enough to be running their own decentralized services.

Heading off the inevitable response: Email is not a social interaction service, it is a message passing service that happens to have social uses.