I would say that it depends on other aspects of the question.
In this particular case, I've closed it. The question in and of itself fails many of the tests that we use to indicate the quality of a question:
- It shows no research effort
- It doesn't answer the fundamental question "what have you tried?"
Because of these reasons, it's been closed as NARQ.
However, there are well-thought out questions which show the above items, it shows attempts that a user has made to solve the problem, or research into the problem as to why they do or don't think it is possible.
In those cases, I believe the question is perfectly valid, even if the answer is in the negative; however, that negative should have equal quality, explaining why the negative answer is justified (simply saying "no" is not enough).