Proof of work allows participants to trust the ledger in a way that is enforced by cryptography, not by law. This creates a powerful deterrent for certain kind

Proof of work allows participants to trust the ledger in a way that is enforced by cryptography, not by law. This creates a powerful deterrent for certain kinds of fraud and abuse. I agree that waste-heat-generating proof of work is inefficient, but that does not mean that no proof of work system exists where the work itself has some positive externalities.