The use of the downvote should come with a corresponding penalty for the person using it. That is the only way to ensure that it is used only when needed, and not abused. Hell, I received a downvote from someone who wanted to collect a possible 10SBD referral fee from Curie. So, he downvoted my post in order to bring its value to below 5SBD and thus make it eligible for submission to Curie. If he had to lose reputation as well as the person he downvoted for having used the downvote, he would have thought twice before using it.