The trickier thing (as with most applied crypto) is going to be who attests and what to.

For press briefing, chaining to something like a White House press root is feasible.

But what about "married congressperson caught in local hotel with fling"? Or in one-party consent states, secret recordings? Self-sign? Sign with news organization (those that still exist) after sharing additional documentation?

I think it may be the true use case for crypto.

Sybil problem still remains. blockchain history can be rewritten relatively cheaply if defense is controlled by an army of nodes under obfuscated control of a single entity or clique. even worse when blind faith is put into authenticity of such information.

Crypto(graphy) already has plenty of use cases. I think you're probably referring to cryptocurrencies/blockchains.

Yes I was using that as shorthand, thanks for clarification.