@mattdm honestly, if we wanted to I don't even think the first one has to be a criteria. As long as the question is answerable (which would be likely if it meets the second criteria you outlined) then it could only be of direct use to the asker, but it would still be of artistic value to anyone else. Now, we might have to revisit that if we get overwhelmed, but that's also something we need to figure out as a community.
I could just as easily see us trying to avoid things that wouldn't be useful for others, but then it also starts becoming more of a technique question with pictures as an example kind of thing rather than really being critique.