RE: What if people start selling their votes?
Sorry but this is dishonest.
"Upvoting yourself for large payouts requires an enormous up-front purchase of SP, and the rate of return on the purchase price is modest while the non-liquid SP gives you huge exposure to Steem."
Or it requires that you were involved in the premine or an early adopter, buying Steem at $0.2 a unit.
So what you're really saying is that it's not accessible to new users.
A Whale only needs to vote on 1-3 posts for them to stand a chance of making several thousand dollars.
They can be paid through a 30% commission based system, so when a post very pausibly floes to $5,000 they may net $450. Iterate thrice = $1,350
Or they can charge $200 per vote, which is fair because if a whale votes on a post, especially by a non-obscure poster, it'll be pretty certain the user will make more than $200.
Iterate thrice $600 a day.
So, no the financial rewards for selling votes aren't very small generally.
This is only true for newcomers.