They would be better off voting (at an optimal time) on a superior post.
They can just work with a group of authors that pay them kickbacks. They can choose the best posts that come out of that group of slave authors. I mentioned kickbacks in my blog post. I've read recently that whales pay 'whisperers' to hunt for the best blog posts for them, so they could be instructed to recruit slave authors. I am not saying any our excellent whales are doing this now. We are talking about game theory for the future.
It seems to me curation rewards make it worse, because the Steeminions have an extra incentive to vote with the whales.
A sham post can easily be spotted and downvoted to zero by other whale/ voters, as that behaviour is against the long term interest of SP holders.
The whale can split up his voting power to hide his activities and/or the slave (kickback providing) authors can produce good content.
RE: Blog rewards CAN’T be widely distributed