Then just like Ethereum, Steem is not a trustless, permissionless, decentralized block chain. But this is expected, because all PoS block chains must be centralized with checkpoints and thus are under top-down control.

Steem is a corporate controlled block chain, which is the antithesis of why we created block chains to remove us from the certain failure of democracy and governance. We need block chains to be immutable and changable by no one after they are launched. I'll be trying to demonstrate a new design for a block chain which has this immutable property (even more so than Satoshi's original design).