Good response. 
Actually, I think the question with regards to unknown unknowns would be something like "Who is a member of the set of unknown unknowns?" The problem is that you can't even know if the set itself has any members or what those members are, because otherwise they're no longer Unknown Unknowns. I suppose that does make it a strange UU, if one at all. Perhaps it's something else entirely? ("known unknowable" maybe?)
Actually, I think the question with regards to unknown unknowns would be something like "Who is a member of the set of unknown unknowns?" The problem is that you can't even know if the set itself has any members or what those members are, because otherwise they're no longer Unknown Unknowns. I suppose that does make it a strange UU, if one at all. Perhaps it's something else entirely? ("known unknowable" maybe?)
