[api]

The great e-mail collapse occurred in the late 1990s and early 2000s when spam made it prohibitively difficult for most users to actually run federated e-mail endpoints. At this point it's an amazing pain to the point that very few attempt it. The rest is moot.

That's the problem with federated protocols. Without someone who owns the system and who has the resources and central authority to police it, if it becomes popular it will be destroyed by spam and other abuse. (Effectively a sybil attack.) Self-policing protocols (without costly proof of work) are an "AI-hard" problem since your adversary is the human intelligence of the protocol's exploiters.

Niche federated protocols avoid this fate by never becoming popular. The other way to avoid this fate is to impose a severe work function like Bitcoin and other block chains, but this is too expensive (figuratively and literally) for most applications. Could you imagine a forum software that requires a minimum of several hundred watts of power to participate in the network?

All others fall to the tragedy of the commons.

[mxuribe]

Alternatively if other/future federated protocols are developed with spam and abuse avoidance in mind, then perhaps implementation of any associated tech stacks could be developed that would be easier for the lay person to stand up/rollout. I'm not saying protocol devs should by default be able to tell the future...but if they go in with abuse-avoidance AND ease of rollout in mind, then that would go a long way for federated-style platform...Or, maybe I'm just being overly optimistic! ;-)

[evgen]

Strong spam/abuse prevention, useful and accessible for most people, decentralized. Pick two.