Are You Nearly Invisible?

From this post from Barbara Ganley:

I realize how lucky I am when I think back to high school, to Exeter's Harkness Table, around which we were given primary source documents, novels and problems to puzzle over together in search of the hows and whys of world events, literature and mathematics. The teacher was there to ask, not answer questions, and the best instructors were nearly invisible and yet always there, helping move us towards understanding how we engage with the discipline at hand.

I know it's probably impossibly idealistic, but I really like the concept of a classroom where the teacher is there to "ask, not answer questions." After all, don't we want our students to be answering the questions? Isn't our job just to come up with really good questions, and then guide the resultant discussion?