@dredmorbius Google Wave
We've even considered doing a show about it.
Looking back now, it was a shift in Google's strategy from "Place we make cool stuff" to profit-focused company that killed it.
Also they chose to release a barely functional reference implementation. But there are still some things in Wave that it would have been/ would be amazing to see in ActivityPub/the fediverse.
emacsen.net is one server in the network