> That would require a central authority to verify signatures.
Nope. Each site would be its own verifying authority. All I care about as a site is that the sites which feed me are responsible for what they send me; all each of them cares about is the same. If any one site gets bad enough, I'll start to reject their articles.
doesn't work for things like email, especially for people who get lots of previously-unknown senders.
> doesn't work for things like email
Which is why I was writing about Usenet☺
Controlling spam in general is a much tougher problem, but in the directed cyclic graph which is Usenet, it could have been done.
And a central authority is not really all that decentralized, is it?