i wouldn’t say that’s true at all. proof of work isn’t the only “artificial scarcity” that we can have... its paying money to compute some thing to get a vote... why not just put money for a vote? or better yet, prove that you have the means to pay a lot of money for a vote.
if you have to hold a lot of limited thing X (that’s difficult to get; eg $10m worth of ETH) on the very chain you’re securing, then that’s scarcity too.
another benefit here is that you can make a trusted network; that way you don’t have nodes coming and going, you have a group of trusted parties with their own network, and there’s less potential for a 51% attack
electricity and work isn’t the only thing that can be scarce
I think scarcity is a bit of a red herring. The key is that it has to be more lucrative to play fairly than to cheat (well, it also has to resist attacks that are simply trying to destroy the service). Proof of work by itself is not enough. It's the scaling of the difficulty to the potential gain -- the implication being that more people mining == more money to be gained by cheating.
The other thing that is compelling about Bitcoin's proof of work protocol is the ideal that every participant is equal. The whole point is to avoid the circumstance where more money means more control. Now, I think we can probably all agree that this didn't pan out -- whoever controls the big mining pools controls the system. I think that if anyone is going to go to the next level they probably have to step back and look at the problem with fresh eyes. Substituting X into "Proof of X" is unlikely to provide the solution, IMHO.
if you have to hold a lot of limited thing X (that’s difficult to get; eg $10m worth of ETH) on the very chain you’re securing, then that’s scarcity too.
another benefit here is that you can make a trusted network; that way you don’t have nodes coming and going, you have a group of trusted parties with their own network, and there’s less potential for a 51% attack
electricity and work isn’t the only thing that can be scarce