Quadratic Voting (2014)
Just reading the linked summary (and not the paper itself), it seems like this doesn't take wealth disparity into account. If the cost for your votes is the square of the votes you want to cast, then that means people with a lot of money can trivially buy significantly more votes than people with very little money, even if they don't necessarily care more about the issue than the people with very little money. It seems like this would change tyranny of the majority into tyranny of the wealthy.