What’s wrong with metaphors?

"Metaphors offer a tiny boost in learnability to first-time users, but at a tremendous cost. By representing old technologies, most metaphors firmly nail our conceptual feet to the ground, forever limiting the power of our software. They have a host of other problems as well, including the simple facts that there aren't enough metaphors to go around, they don't scale well, and the ability of users to recognize them is questionable.”