Adam,
Just found your post. Great article.
I am baffled by the banks' interest in blockchain.
They appear to have swallowed the hype - as they did briefly with Quantum Crypto - another solution in search of a commercial problem.
Much of bank claims of what will be achieved with blockchain, e.g. trade-finance documentation chains, can be equally well achieved with good quality PKI. Banks invested in solving operational and legal/contractual problems with PKI, e.g. by investing in Identrus, establishing clear liability and mandating key management, hardware key protection and revocation management through OCSP. Yet they appear to have left much of this investment on the shelf and now waste shareholder money on this shiny new technology to solve problems they've already solved and forgotten about.
OCSP (Online Certificate Status Protocol) was an interesting lesson from PKI that has parallels to the fraud correction example you provide for block-chain. To make practical something that is essentially a decentralised / offline service you ended up needing an online/centralised service to check the data hadn't been corrected/revoked since it was agreed.
If you want a revocation mechanism for distributed ledger you need central real-time infrastructure to operate it, rendering a distributed ledger pointless.
Without a revocation mechanism you have a 'bearer instrument' which is then problematic for money laundering.
