The thing is, game theory doesn't really cover the present situation here as far as the conclusion that this abuse is inevitable given the current system.  There is so much power concentrated in the hands of the few that it would really only take a couple or even possibly only one of the largest accounts (hello @freedom) to remove their delegation(s) from vote sellers and use thatSP to flag vote buyers.  I doubt it would even take one week before the whole thing crumbled.  Major vote selling could be stopped in an extremely short amount of time.  The question is just how bad will things have to get before the biggest guns wake up and smell the coffee.  Obviously a fundamental flaw of Steem is the assumption that the largest stakeholders will act with the best interests of the network at heart to protect their investment.  But they have been so ridiculously succesful in concentrating power in the hands of the few that they do indeed possess equivalent power to a centralized governance like Facebook has that could easily prevent this kind of abuse.  They just have to choose to do it.  I think at some point the present course will present an iceberg that the biggest whales cannot avoid.  It is just not sustainable.