While I agree this side of the argument has a valid point (for instance, driving away certain users), there is a counter argument that is exactly the same: driving away users.
The success of the site is not in the amount of question askers, but also in the amount of answers and the quality of those questions. Sure, stackoverflow drives away some users, but it also keeps some high value users that answer interesting question.
There is very little worth in drive-by questioners and help-vampires that just ask one super-duplicate question to get a quick answer: but the effect it has on other people can be that they keep on seeing the same, uninteresting question, and don't bother to come back and help anymore.
You need to stop all these bad questions to come up, and yes, downvoting and closing is a tool for that. Keep in mind that this is not a forum where you can just open a thread for yourself, the goal is to obtain valid knowledge in question/answer form.
So yes, I agree that this 'behaviour' is bad for some (e.g. the new users who did not read the FAQ, are not providing interesting/new questions or do not bother to put in some effort), but it protects some others (interested parties) who are willing to answer complitcated problems and help make this site a repository of knowledge.
