All I want to argue is that, at best, this is a slim advantage of a video over a book. So we shouldn't be saying that Khan Academy is revolutionary in any meaningful sense. It's a new medium for the same old content, and it's a medium whose advantages are pretty slim, at least for the way Khan is using video.
Sure. I'd even agree. I would say that for certain use cases, the advantage of video can be large. Averaged over all use cases that matter, there may be no advantage at all. Of course that doesn't mean you shouldn't use it where the advantage is large (not that I think you're saying that!)
