I have done that very same activity with students who were exploring the use of metaphors in Information Systems Development (you use a metaphor then see where it breaks). I often used teaching and learning as a context for class activities because of its shared nature within a class (students and teacher). I asked them to imagine that they were IT consultants starting to think about using technologies in learning and teaching, then come up with some metaphors. It was very interesting. Most of the metaphors they came up with cast the teacher as active and the student as passive eg in a restaurant where the teacher was the chef and the students were the diners. The most interesting part of the activity was the discussion we had afterwards about active/passive learning and role of tech in this.