Proof of work prevents small attackers to do that, but attacks with large computing power are not going to prevent this. Unless you made your proof of work rea

Proof of work prevents small attackers to do that, but attacks with large computing power are not going to prevent this. Unless you made your proof of work really hard, but then not a lot of people can participate. What you need is a participation treshold to be hit before someone can vote. Kind of like HN limits your downvote until a certain karma threshold.