There are active discussions around both meta and several TCS questions about what questions should be rejected. The two reasons most often stated are (afaik)
- too basic (aka too localized, whatever that means)
- homework problem
There is a multitude of opionions about wether or not these reasons are legitimate or not; I do not want to discuss this here. Let us assume they are (seems reasonable since there is a large faction in favor of them). But then, should we not also close questions like these:
- Counting the number of Hamiltonian cycles in cubic Hamiltonian graphs?
- Complexity of simplex algorithm
My rationale: These and other questions that are phrased like "What is best ... known?" or "Is there ...?" are "only" a replacement for literature research. They do not pose a motivated, original problem or reflect that work has gone into finding an answer. One could say the one asking has not done his homework.
Of course they are research level questions and therefore inherently more interesting -- and they offer a possibility for experts to show off (in a good way), other than undergrad homework problems.
Nevertheless, I feel that a general rule of thumb for question scope should be found and that the negative approach (finding criteria for closing/rejecting) cannot go anywhere.
So, let us try to answer the following questions: What makes a question good? What questions should not be closed?