As far as economic incentive, is a million dollars really that much? If a government comes to you and says here have $10 million in cash you wouldn't hand over your masternodes? What about $50 million? I sure would. There are plenty of other cryptos to get behind. The entire marketcap of Dash is less than $25 million as we speak. The attack I've described would be trivial for somebody with a little bit of cash and motivation.