I am a huge fan of Vygotsky, and think it's great the impact of mediation that he identified with language has now been applied to technology. However, I don't think he had so much to say about the 'learning of the teacher' (but would love to hear about it if he did).
Anyone who has been a teacher will know of the moment when one's own understanding leaps as we explain something to another see
http://www.google.co.uk/search?hl=en&num=20&ie=utf-8&oe=utf-8&q=learning%20through%20teaching