@luna Reminds me of a social media idea I had lying around in the back of my head when I considered this problem. It involved clients managing their own local feed and then passing it to either an 'aggregator' to coalesce it with others for ease of discovery by other clients (matching the purpose of an 'instance', but without having to have your account there and deal with migration when you want to leave), and/or 'relays' for direct comms between two mutual parties (in order to allow people with the ability to manage servers to contribute to keeping the network running without having to resort to *everyone* having to be a sysadmin). When you don't want someone or somewhere to see your posts, you just, well, don't send 'em.

... Considering this is effectively just RSS with extra steps, though, I get the feeling that's probably what's gonna happen. Someone makes a specialized RSS client with good microblog social media UX and a couple infrastructure bundles anyone can set up, and markets it like a new platform, bam. they win.