I think there should be a quota or similar system on downvoting. Numerous times my posts or questions have been downvoted, without a comment on how to make it better.

My suggestion is that after X downvotes the user is required to post a comment otherwise they are not allowed to downvote after Y amount of time.

Or another thought that came to mind is that when someone downvotes it takes one rep point away, well, what if the user got the rep back by posting a comment. And in order to encourage "quality" posts, if a comment gets removed (due to the lack of quality) then the user loses more than one point.

I am not saying that downvoting should be discouraged, because sometimes I am wrong and would like to told why I am wrong and what I need to change to make it right, but encouraging downvoting without a response only spells trouble in my opinion.

My two cents anyways.