Except for pubs, which are helpful broadcasters of both private and public stuff, but it makes sense to host them on an infrastructure that can ingest 70 GB a day and have a couple days of retention
Pubs don't follow everyone on the network. People set them up and give out invites to their friends.
Which means even less requirements for such "private" pubs. However if SSB is ever to replace Twitter, I would guess there would be other, "public" pubs that try to get all the content possible.