[nybble41]

> A secure distributed ledger of financial transactions does not inherently need nearly this much computational power to maintain, as is evidenced by Ethereum's impending move to proof-of-stake.

You can claim that as evidence after Ethereum has actually moved to proof-of-stake and operated in that mode for a significant length of time without any notable vulnerabilities. Proof-of-stake has some known drawbacks compared to proof-of-work; in particular, at least in naïve implementations, there is nothing to prevent a malicious party from staking the same coins in multiple chains (forks) simultaneously, a flaw which proof-of-work systems are specifically designed to avoid by making the proof depend on each chain's history. One assumes that the Ethereum developers came up with some sort of mitigation for that issue, among others, but it has yet to see real-world testing with significant funds at risk should it fail.

[MereInterest]

I'd claim traditional databases as an example of a secure distributed ledger of financial transactions. Every single credit card processing network does exactly this. What cryptocurrencies do is add "trustless" as a requirement, and that's where the power consumption comes in. I also think that's a weird requirement to have, precisely because treating every interaction as adversarial introduces so much overhead.

[nybble41]

The requirement exists regardless of how hard or easy it is to implement. "Trustless" is a requirement because history shows that there are many circumstances where existing payment networks cannot be trusted. Payment networks sometimes refuse to do business with certain parties merely because it's not profitable due to bad credit, a higher-than-average chargeback rate, public relations, or other reasons. Even when the networks themselves are not actively antagonistic, they are vulnerable to political influence which may take the decision out of their hands.

Where trust is feasible transactions can be settled cheaply in separate records and not on the blockchain itself. The Lightning network is one such protocol; support for inter-account transfers on the same exchange is another. However, it's good that the trustless option exists for the cases where trust would not be justified.