Take your pick:
- The FAQ explicitly rejects list questions. Therefore they are “off topic: Questions … are expected to generally relate … within the scope defined in the faq.”
- Questions expecting a complete list for an answer are overly broad (you can't expect a single person to provide an exhaustive list), which is one of the conditions for not a real question.
- Questions expecting a list of items (one per answer) or questions expecting only a partial set of answers (such as “is there an example”) are “not constructive: … not a good fit to our Q&A format. We expect answers to generally involve facts, references, or specific expertise; …”
The reason why the FAQ forbids list questions is not because we think they don't relate to the topic of the site; they are not off-topic in that sense. But we've found through experience that they do not lead to interesting answers. This fits the broad definition of “not constructive”.
I prefer to use “not constructive”, especially with askers who are new to the site, because closing a question as “off topic” and “not a real question” automatically casts a downvote on the question, but “not constructive” doesn't. The reasoning behind that downvote is that “off topic” often means “why did you even think to post that here”, and “not a real question” often means “what's this drivel”. “Not constructive” is more subtle; often questions that are “not constructive” could fare well as initial posts on a discussion forum, but don't work as questions expecting answers.
I'll take this opportunity to go through the various ways list questions are asked:
- What are all the works with feature X? Only complete answers need apply.
- What are all the works with feature X? One work per answer please.
- What are some works with feature X?
- What's an example of a work with feature X?
- Are there any examples of a work with feature X?
The answer to the last question is invariably “yes”. The answer to the first question is invariably impossible to establish because no one knows all the answers (if it is possible for a single person to compile the answer, then this is not a list question, it's a factual question).
The formulations in between invite a large set of answers where everyone contributes one example at a time. The result is not a set of answers, it's a set of items. The voting reflects primarily who posted first, and also to some extent which works are not popular. How adequate a match the answer is for the request doesn't figure in the voting, as a rule. We had a lot of such questions in the early days of the beta on the site; question 1 is an example we've kept for posterity. When you go through it, please keep in mind that this is the best response we've had to a list question.
I discern a pattern where people who've seen lots of list questions hate them, and people who haven't love them. For example, I was initially rather in favor of allowing lists, with some requirement that they shouldn't be too broad. Yet I was concerned by their large number. Now, I've become dead set against list questions. Not that I don't think they can be interesting, but they don't fit on Stack Exchange. (Whether we can find a home for them in another form, perhaps on another site, should be the topic of other meta discussions.) A less personal data point: on our jumbo on/off-topic list, list questions were initially one of the most downvoted items, and has now gathered a few upvotes. It seems to be an acquired distaste.