This question has five downvotes, and was closed as a duplicate of a question with 25 up-votes. Should one down-vote a question merely because of duplication? There's no mention of anything wrong with the question besides duplication.
Later note: Maybe this will help clarify things: I think in some cases it is appropriate to up-vote a question and also vote to close it as a duplicate.
One of comments was "This is easy to google". If entering the title of question into Google search returns an answer in one of top results [which is the case here], I'd be tempted to downvote the question as unnecessary and not showing due effort on the OP's part. (As a matter of fact, I did not downvote this one).
Duplication is a red herring.
I speculate that the quality of the question writing is the primary motivator for the down-votes. If the fact it is a duplicate has any relevance at all, I doubt it's more than simply being the final straw that tipped one or two people over the line from not caring enough to finally pressing the arrow.
Alex Becker, at least, has confirmed this is the reason for his vote in the comments.
I have to admit (and hate to think it might be true) my suspicion is that one reason for the astounding downvotes in this particular case may be that this particular poster has drawn attention to him an a rather unlucky way, by posting questions some members here consider as not appropriate and target for downvoting and voting for close, in particular when the education of that poster (which he indicates in his profile) is taken into account (this last remark is extracted from the comments to some of the posts from that person).
As an example, in another thread one of this members questions was closed with the reasoning that it is "not a real question", which, if you look at the explanation to that reason for closing a posting, does in no way apply to the question asked.
I do get the impression (and I'm unhappy about it) that some people here sometimes tend to react out of some prejudice they acquired by previous postings of someone else -- or even other sources -- and downvote or vote to close out of some automatic state of annoyance, without looking in detail at the particular question they react on.
This is one of the reasons that I'm also unhappy with the fact that downvoting is anonymous (voting for close is, luckily, not). I rarely downvote and if I do, I take pains to make clear and transparent why I do this. I actually consider anonymous downvotes of questions as cowardly (my view with regard to answers is a bit different here ;-).
I feel duplication is a valid reason for closing. We do not need to have 8, 15, or 100 copies of questions such as "why is 0 even?". We do need to have at least one good answer to the question. Once we have a collection of one or more good answers, closing future duplicate questions points everyone to the answers that are already given. That gives them faster access to the good answers and prevents duplication of effort when others might spend time posting the same answers. Of course anyone who wants to post another answer can still do so on the original question, and if they want a clarification about a specific point they can write a more detailed question that is no longer a duplicate.
