It is most certainly a reasonable consumption for a payment system. Every society with inflationary money eventually grinds to a halt and crumbles. The world mu

It is most certainly a reasonable consumption for a payment system. Every society with inflationary money eventually grinds to a halt and crumbles. The world must absolutely have the best implementation of money that it can get its hands on. Energy use is not its defense against attacks. Distributed hashing is. The hashrate can be much lower and Bitcoin would still work. The difficulty would adjust downward. Obviously, the hashrate will top out at some point in the future. From that point on, it can dwindle and that won't be a problem. Just so long as a certain minimum amount stays around to keep the network running. That won't be a problem in a future where Bitcoin has become the new global currency.