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I'm not a fan of the downvoting feature in general; frankly, I think it should be removed from all of the stackexchange sites.
Negative feedback leads to negative results. I recognize that the intent is not to provide a means of giving negative feedback, but that's what downvoting does. "The community's way of telling peers that their content can be improved" isn't an accurate description of downvoting: people who downvote other people with no explanation as to why (the usual practice) generally consider them not their peers, but their inferiors.
I fear that the downvoting feature panders to the worst aspects of human nature, to an extent that far outweighs any possible benefit that it can provide. I recognize that the intent of downvoting is to make a form of constructive criticism available, but that it fails to do. It simply says "this is bad" without any explanation. If someone really wants to offer constructive criticism, he can do so in the comments, or by closing questions with an explanation of how to bring them up to par. If he does that, it is that that has the value, not a downvote that might or might not go along with it.
I submit that the increasingly negative "elitist" reputation of many of the stackexchange sites (stackoverflow, the "bread and butter" site, in particular) is due more to unexplained downvotes than anything else: downvoting is (much) more often than not a way of telling new people that they aren't welcome in the club. This isn't conducive to growth.
It seems to me that the recently introduced admonishment to "be nice" to new members acknowledges the problem without really doing anything about it. It would be given more teeth if the downvoting feature were removed entirely — people have to give a lot more thought to a comment than a downvote decision. Furthermore, the (apparently many) "serial downvoters" who contribute little if anything else to the site would take themselves elsewhere.
Thoughts? What are the positive contributions (are there any?) that downvoting makes to the stackexchange sites?