This has come up in the past, but then the answer was that the website was in beta and needed to be "seeded" with good questions, so it didn't matter. Now that the site is well out of beta, what do people think of questions like this?
I am not in favor of questions to which the OP knows (or thinks s/he knows!) the "entire" answer. There is a fine -- but not invisible -- line between a site where people ask questions and a site where people pose problems and puzzles. Especially, in the former instance I would like to think that by answering I am helping some particular person out, but I cannot see how to feel that way in the latter instance.
It is of course perfectly good to know one answer to a question and ask for other answers (ideally satisfying requirements to be enumerated by the OP) and so forth.
Official SE policy is that it is okay to ask questions to which one knows the answer. For example:
Intent is not an element of the validity of a question. It's perfectly valid to ask and answer one's own question, so there is no inherent prohibition on asking a question to which one already knows the answer.
The critical points are the same as for any question on any SE site: Is the question on-topic and worthwhile? If so, keep it. If not, can it be revised into one that is? If so, do it. If not, close the question.
It could even be that there is a new way shown how to arrive at the solution - or even a generalisation and/or new connection. So if the question is valid and interesting everybody will learn.
So I think it is ok - in any case you won't be able to tell if somebody did not say (s)he knew already, so the discussion is also a little bit academic.
Just a curiosity, guys. How does your policy about questions whose answer is known to the OP work?
Until now, I wasn't able to figure it out: in fact, while a post of mine was closed in a flash (and used by Isaac here, to give an example of what should not be allowed on this forum), none of you opened a poll to close this one; on the contrary, that post got even two full answers... So, how comes?
I don't think it is a matter of using/not using the tag puzzle (for I didn't use it), isn't it?