If you are to do a truly high quality screencast, you would need to have a script (and code) written ahead of time anyway. Otherwise you would fall afoul of the other complaints in this thread -- overly long, rambling and unfocused.

Interesting idea. I'd be curious to hear if they turn out a good transcript or whether their lack of understanding of the subject material makes it garbled. I guess with enough people doing it, you can check out the most common transcriptions and go with those...