Well in my opinion there is a big problem with downvoting. Most people who get a downvote just go to the downvoter and give him a downvote too on one or all of his posts. Thats what makes it very hard for small Accounts to downvote a big Account, because they will lose all their rewards.
I think the only solution to solve that problem is to create a second Account that does not post but only downvote bad content.