I thought I had it (mostly) solved with fediverser: users would go to one place, sign up with OAuth to the service they wanted to leave (Reddit, Twitter...) and the system would behind the scenes create an account on any of the participating instances. In doing so, it could leverage the user existing information (subreddits subscribed, users followed on Twitter) and find the corresponding subreddits/users that are already registered.

Turns out the biggest challenge was not in getting users, but in convincing admins to join the network. Instances with open registrations are already dealing with spammer accounts, and none of them was excited about the idea of this extra vector for having unvetted users on their services.

This doesn't mean that centralized services are safe, though. I am reasonably convinced that we can have "social media" that is less focused on "platforms" and more like what we (used to) have with web: companies and institutions owning their presence by running ActivityPub "servers" on their own domain, and a hotch-potch of community/commercial servers to serve the users who want "basic access".

But to get there, we need to stop thinking that the way to get rid of Facebook/Twitter/Reddit/Instagram/YouTube is by taking their templates and tacking "but federated!", and we need to really come up with a killer app on ActivityPub (or Solid, or Linked Data, or ActivityPods) to disrupt the whole thing entirely.