He's right, though. Bitcoin-like cryptocurrencies are stupid. People even continue to use Bitcoin Gold, despite the hackers being able to repeat this attack at will. And the enormous amount of resources being destroyed to power Bitcoin is indeed an environmental disaster. The actual power lost due to cryptocurrencies is imaginary, too. Law enforcement has become good at tracking transactions as anonymity has never been part of the design.  http://fortune.com/2018/05/29/bitcoin-gold-hack/