Given that blockchain is exclusively a workaround to lacking a trusted third party, approximately what fraction of economic activity would be revolutionized by not having to trust anyone?

I'm under the impression that many of the blockchain-ers see it more as a new internet and less of a means of executing "trustless logic"

Well, it's grossly inefficient, so in that sense it's in the spirit of the web.

Yeah to add to my above comment, I don't see why anyone would think it's "new internet" or use it in any non-subversive use case

That's the exciting part. We don't know. Read Neil Postman's writing.

Yes I agree. Blockchains would be pretty useful for many scenarios. Few ideas (some already in prodcution):

- supply chain transparency (with the right crypto model you can do things like that different parties have different visibility into transactions)

- food traceability

- fighting counterfeit items (on amazon!)

- a review website where reviews cannot be tampered with (bye bye google or amazon removing negative reviews)

- logging stack for IT operations that cannot be tampered with