This assumes there will not be well-monied beneficial actors who more than even it out.  Hostile actors would  not be able to significantly harm the system though because others could similartly power up to help mitigate against it.  

If Bob has 1 billion dollars in whalepower and is hostile toward the system, and John has 1 billion whalepower used to reward top content creation guilds who I have helped create by watering them and providing them with more resources, John would have an army of content producers who earn steemusd.  If bob attacks effectively and harms the value of the steem token, these armies of people are going to collectively earn and store more Steembacked dollars than bob.  They all buy Steem and power it up to get more steempower (not even whalepower) as they watch the hostile actor's strength in the ecosystem wane over time.  Why? Because after even a successful attack on the network like this, the hostile will have had their account outed (and it isn't like they could transfer whalepower to another account), which will mean the accounts reputation will be Horrible and all serious steem users will know them and most will actively work to ensure they can never effectively pull off attacks again.  John will have an army of people paying him out with numerous smaller tx's while they will ignore the attacker.  And the attacker will not have the power again unless they are willing to buy/earn more steem to lock away forever (aka burn).