I think Joe's analogy with the librarian is a good one, not sure how we can formulate and enforce it in more general terms though.
Also I have previously asked another questionanother question asking for ways to find a specific statistic, which is among the top 50 most viewed questions we have on the site.
I think we should be careful in not limiting the site too much, it might end up becoming a site for "explain this rule for me", to which the only feasible answer is to take a citation out of the rulebook.