[babyloneleven]

Also, if you rely on a third party to do identification for you, you simply don't need a blockchain.

Blockchain is heavily constrained by the vital requirement of not trusting any third party whatsoever. If you relax this, you can build much simpler systems that are equally secure regarding non-repudiation and other properties but doesn't need proof of work.

[toomuchtodo]

Blockchain has one genuine purpose: value transactions where you can't rely on societal legal framework, nor do counterparties trust each other. "Silk Road".