Aye, agreed that "few but large" entities are definitely a threat if used maliciously. The large difficulty is making deterministic "stake/reputation" systems that do not rely on monetary backing. In crypto, the only TRULY deterministic source of "stake" is the currency itself, so, the more of the currency someone holds, the more powerful they are...
It's far from perfect, but many are working to try and improve these systems day after day, I have alot of hope for this space.