- PoS is not "decentralized" nor "democratic", because it means that only those with capital can participate in the network consensus building. This is "technically correct", but (a) it ignores that existing PoW also require massive amounts of capital to deploy mining facilities and (b) it is not democratic because only those with access to cheap electricity will profit from being a miner.
- PoS implies that those staking their crypto are "investing" with their tokens, which would make the token a "security" and not a "currency". This distinction could make it easy for the SEC and governments to intervene and create regulation that would require stakers to only participate if they implement changes at the protocol level. E.g, it could happen that a staker would reject to validate any block containing transactions to smart contracts that got sanctioned. This is a more real concern, if you think about all the big players (read, centralized exchanges) who are staking ETH on behalf of their customers and therefore will have non-negligible control over the network. In this case, the community expectation is that (a) users of staked ETH pull out of the exchanges and run their own validators and (b) the exchanges realize that they will be shooting themselves in the foot, and therefore go on to fight whatever legislation that pushes on that type of control/censorship at the protocol level.