> 1) Proof-of-work systems are pure, unadulterated energy waste (and an ecological disaster as long as we depend on fossil fuels). They cannot, ever, be allowed to become significant in the economy, lest our future will be building a Dyson sphere around the Sun just to power everyone's ability to pay for a hot dog on their way to work.

> 3) The main users of cryptocurrencies are (AFAIK) criminals and amateur financial speculators.

The problem is that to fix this, we need governments to wrap their heads around this.

Cryptocurrencies exist as a thing that allows people to engage in pseudonymous financial transactions over the internet. It's going to be really hard to put the genie back in the bottle. Particularly for black market transactions, because then you can't even ban the currency since they'll just ignore the ban on the currency at the same time as they're ignoring the ban on the product the currency is being used to pay for.

Which means that the best thing we could do is out-compete it using a more traditional financial system. When the existing KYC laws have already been voided by the use of cryptocurrency, just admit the loss, stop yielding a competitive advantage to the system which is destroying the environment, and let people have pseudonymous bank accounts and smart contracts and so on, in ordinary banks and based on the trust in ordinary banks and governments rather than the trust in proof of work.

That would destroy the utility of cryptocurrency, and it could be the only way to really do that.