If you ask someone knowledgeable a specific question, they can frame the answer (and question) in the right context, customized for you and your question, and make you see the big picture. Also, you can follow up with more questions until you understand. It's easy to read something and completely miss the point (unless it is very well presented) because there is no interaction.
It is certainly valid to claim that one can learn things this way, but it hardly seems to be the purpose of schooling. If I could read a 45 minute lecture in 7 minutes, I would then have an additional 38 minutes of question time. It's even more inefficient to sit in a classroom full of people, listening to "customized" questions asked on subjects that you fully understand. The scenario that bugs me the most is when a fellow student asks a confused question that indicates to me he has understood very little of the lecture, the instructor then proceeds to answer it poorly, which then confuses other students.
