Recently, the question Was Eric Flint's 1632 the ONLY prominent SF&F work/universe where some (approved) fan fiction is officially considered canon? was asked.
The question asked for a single example, in order to avoid being a list question (list questions are considered a poor fit for this platform, and are considered not constructive by definition).
I feel that if the answer is "yes, Eric Flint's 1632 is the only SF&F work/universe where some fan fiction is officially considered canon", then the question is too localized, as it reflects a single point in time (all it takes is one other franchise approving fan fiction as canon and now the answer is incorrect).
If the answer is "no, there are others", and then we explicitly limit the answer to a single example in order to bypass the list question issue, then the answer isn't terribly interesting, and, by extension, neither is the question ("here's the only example of a franchise that includes fan fiction as canon" might be somewhat interesting, as it represents a unique situation, but "here's two examples of franchises that include fan fiction as canon" does not seem interesting).
I perceive this as a limitation of questions that look for a yes/no answer, where the answer can be proven by a single example. However, that doesn't mean that there could not be other questions in this format that might be of more general interest.
Do we, as a community, feel strongly one way or another about these types of questions? If some should be allowed, what are the criteria of identifying good questions from bad? Or are questions asking for a yes/no answer based on a single example not a problem?