An open protocol sounds like the only sustainable solution that protects privacy. Are there any other popular, open protocols in the wild?
Fully realtime, can handle huge load, several serious servers out there, interesting clients. XMPP can do IM, but it can also do social networking (https://xmpp.org/extensions/xep-0060.html XEP-0060: Publish-Subscribe, https://xmpp.org/extensions/xep-0277.html XEP-0277: Microblogging over XMPP) for many years now.
I'm working on Movim a social network fully relying on the XMPP protocol http://movim.eu/, we already have many nice features social and IM wise.
Remember it is not just public posts which you should be concerned about...but it is your interaction with the sever as well, as well as your semi-private communication.
Ideally we could also encrypt all our posts and whatnot so the server operators can't snoop as easily.
Because you don't have to join coolsocial.fake to view my social media posts, it's a lot less likely folks will concentrate on one platform and it will make ditching that platform a whole lot easier.
Making it easy for people to leave also forces server operators to avoid doing/not doing things that would cause people to leave.
That way Ted Cruz and even Bernie Sanders would have an equal access to materials, and individuals would more informed that everything they type on their keyboard is there to stay.