Khan Academy is videos of lectures. This is nothing new. They are boring and do not allow the student to interact with the lecturer. They also focus on solving a math or science problem through basic steps, but do not focus on the actual theory behind the problem. The student may be able to solve that problem, but can they apply the concept to other problems and situations? Many of my students who have watched the videos say that they are boring, and even confusing at times, and that they would rather have me show them.