Sure, any energy expenditure over and above what would be necessary to run a centralized database can be considered inefficient, and therefore "ecologically unf

Sure, any energy expenditure over and above what would be necessary to run a centralized database can be considered inefficient, and therefore "ecologically unfriendly". However, the hashrate isn't burning energy for no utility: the security of the network is directly proportional to the energy expended in hashing. Considering that the energy is being expended for a purpose (security against malicious actors), and that it is economically infeasible to expend more energy than the marginal fee revenue in a given moment (once we transition from the current block subsidies to a pure fee market), I question whether calling mining "economically unfriendly" is fair. The energy usage will scale linearly (not exponentially) with usage, which seems perfectly alright to me.