It's not that. It's the rich will have untouchable anonymous power. There is no way to stop a cabal of people from taking permanent control and reversing transactions discretely.
I think you were already answered:
Wealth PUT AT RISK PROTECTING THE NETWORK = stake.
As soon as the cabal that holds 51% of the stake in PetkoCoin starts cheating, the trust in PetkoCoin will fall, a new currency - CBeastCoin - will appear (probably with same source code), and the cabal will lose the real-life wealth they have invested in PetkoCoin. This is what guarantees that the cabal (if any) will not be malicious. Of course, it is out of question that the currency software should be open-source (IMO).