I just showed this to a group of teachers today, during a professional development workshop on wikis, and they really responded favorably to it. In fact, they talked about possibly using this type of how to animation as an expository writing assignment for English students.
MT - very cool - I think this is one of the best illustrations of the concept behind wikis ever! iMovie is great for animation! There is also a series of of animations created by the Royal Society for the encouragement of Arts, Manufactures and Commerce (RSA) - see this one about public ed by Sir Kenny R.