someone235

Btw, this is one of the reasons they wanted to revert the DaoHack - they didn't want a malicious entity to hold 5% of the stake

If someone has 30% of the stake, he can keep his share forever if he wants to. If someone has 30% of the hash power he has to keep innovating and keep up with the competition to keep his share. This kind of dynamics makes PoW permissionless, since you don't need cooperation from other miners in order of joining the game.