I particularly liked this: "Although the use of metaphor may ease learning for the computer novice, it can also cripple the interface with irrelevant limitatio

I particularly liked this: "Although the use of metaphor may ease learning for the computer novice, it can also cripple the interface with irrelevant limitations and blind the designer to new paradigms more appropriate for a computer-based application. The designers of the Phelps farm tractor in 1901 based their interface on a metaphor with the interface for the familiar horse: farmers used reins to control the tractor. The tractor was steered by pulling on the appropriate rein, both reins were loosened to go forward and pulled back to stop, and pulling back harder on the reins caused the tractor to back up [5]. It's clear in hindsight that this was a dead end, and automobiles have developed their own user interfaces without metaphors based on earlier technologies. Nonetheless, people today are designing information-retrieval interfaces based on metaphors with books, even though young folks spend more time flipping television channels and playing video games than they do turning the pages of books."