Depending on the implementation of PoS, there could be all kinds of incentives or pressures for a lot of distributed computing power to get thrown at it, despite it only needing a fraction of that.

None of that is a problem if the system is #1 displacing other higher consuming systems and #2 not actively harming people.

Re: #1 So far most of what I've seen out of blockchain seems additive - it's not replacing old systems, it's layering on new systems. But it's still early days, maybe that'll change.

As for #2, well, it's hard to trace the exact benefits and harms of blockchain we've seen so far. Which leaves me to fall back on history. You can call me a commie if you want to, but a system that benefits capital over labour usually shakes out to benefit a few while harming many ¯\_(ツ)_/¯