I like the idea of using podcasts in the classroom because it operates under the same principle as having kids post to a blog instead of sending you their work. The work should be better because a wider audience is viewing it. I think that it helps kids think of real-world applications for their thoughts and assignments and gets them out of the bubble that is their classroom.
I also like the fact that, if they do a good job, teachers in other parts of the world might show it to their classes to teach them a concept. I think that hearing it from someone their own age ads an interesting dynamic to education if the podcasts are done well.