This is one of those times when I post without having looked into things carefully first, which means I run the risk of rehashing well worn ground or the like. However, I'd rather post this, and have someone link me to a good discussion of it than let the blog stagnate (especially after I officially declared an end to the hiatus and promised a post today).
This is something I've been thinking about since watching an episode of the West Wing in which it (sort of) came up.
When someone asks "Do you know the time?", it is rarely, if ever, the case that a correct affirmative answer to the question would be satisfactory.
At one point in thinking about this I was wondering if maybe a maxim of courtesy was in play, something like, "don't ask a question which you lack sufficient evidence to believe that others in the conversation will be able to answer." That formulation requires tweaking if we consider "I don't know" to be an answer to the question "What time is it?". It's also possible that such a maxim would be superfluous, and existing machinery can already explain what's going on there.
The phenomenon seems to be potentially related to what goes on in situations like this: "What time is it?" "I think its around 5", where the "I think" serves to generate an implicature about the speaker's confidence in that guess.
I haven't really looked into it any literature on implicature and questions, but investigating issues for implicature that are specific to the domain of questions is something I want to do in my spare time this semester (if I have any such time).
If you know of anything good to read on, or related to, this subject, please let me know.