There are some questions, where the OP is trying to do something which is, frankly, impossible and absurd. The fact that usually makes it impossible is that the OP insists on refusing to use other techniques, or to change his strategy etc.
Now, if more than 10-20 experienced SO users highlight the fact that the OP's goal is simply impossible, should the question be closed down?
I think the right way to deal with this is just to straight-out answer the question saying that it's impossible and give your reasons.
If the OP stubbornly disagrees, so what? 10-20 experienced SO users will agree with you, you'll get a swarm of upvotes as an "in-your-face" to the OP.
EDIT :
And if it does turn out to be possible in the future. (say someone posts a late answer) You might have a chance of getting a Populist badge out of it. :)
"You can't do it" technically is a valid answer. If the problem is so specific to the asker's situation that nobody else is likely to have the same issue, then the question should be closed as "too localized". If there's not enough information to go on, it should be closed as "not a real question", and so on.
Otherwise, there's no harm in leaving it open regardless of the fact that there's no accepted answer or other acknowledgement from the asker.
See also: What is an acceptable answer?
I disagree. Just because the OP wants to do something that is impossible doesn't mean that it can't lead to producing useful information for him, or indeed, solving his problem in another way.
Now, if more than 10-20 experienced SO users highlight the fact that the OP's goal is simply impossible, should the question be closed down?For some reason I think you need to read up on Galileo Galilei.