[davepeck]

I’m not sure that Bitcoin offers any special insight here.

We use email; it’s very much a crypto-less federated system that works at scale (of, more or less, every Internet user!)

And there are newer examples: while it’s by no means a Twitter, Mastodon (and the broader ActivityPub universe) is already at a healthy scale. I collected these stats three and a half years ago; the ecosystem has grown substantially since then: https://davepeck.org/2018/05/03/mastodon-stats/