There is one thing: decentralization, and there is another: concentration of ETH ownership. Concentration of ownership means a few entities own most of the ETH

There is one thing: decentralization, and there is another: concentration of ETH ownership. Concentration of ownership means a few entities own most of the ETH. Up to a point (where one entity owns all the ETH, and therfore ETHUSD goes to zero), who cares, as long as there are still enough token in circulation to conduct business? Decentralization OTOH means that no one can prevent me from executing a transaction on the chain. With POW, these two things are basically unrelated: concentration can be arbitrarily high, I can still transact. However, IIUC, with the aptly named POS, concentration of ownership brings concentration of voting power and therefore large holders become theoretically capable of censoring transactions ... not great. And I don't believe there is any mechanism in place to prevent ownership - and therefore voting power - to reach arbitrarily large levels.