That's what I've been thinking: why not replace (or supplement) the videos with plain old html with embedded pictures/video/response forms as necessary?
In a Udacity course I took (the driverless car one with Thrun), they did have a (community-generated) html version of the lectures, but you would still have to go back to the videos to get credit for having watched them and answered the questions -- and, of course, it was always a work in progress.
The advantage over textbooks would be in a) hyperlinking, and b) a known group of people doing it at the same time as you so you can discuss the material and get answers from the professor on the most common questions.
In a Udacity course I took (the driverless car one with Thrun), they did have a (community-generated) html version of the lectures, but you would still have to go back to the videos to get credit for having watched them and answered the questions -- and, of course, it was always a work in progress.
The advantage over textbooks would be in a) hyperlinking, and b) a known group of people doing it at the same time as you so you can discuss the material and get answers from the professor on the most common questions.