Yes, there are a few existing decentralized social networks but as far as I know, they have not thought about or focused on some of the privacy-related issues that we want to highlight.
Shouldn't you at least mention once in your post that this is bit similar to diaspora? Or at least write a bit in there to say what your proposing does better than diaspora
The post was meant to be a concise description of an architecture, and is not meant to be comprehensive in any sense. I definitely agree that diaspora, and a few other projects out there feel like they should be a part of it and in fact, it started out as a more extensive post including a roundup, and a motivation on the state of social networks. Hopefully, it is the first of a few written works (as well as technical works) and there is plenty to be said about the topic.