Charles Miller has a great shot of XP-style cards in use, tacked up on the Wall of Death. As he describes:
When, as we do, you write your specs on a wiki, keep track of your development tasks in an issue tracker, and eventually ship products that only exist as bits downloaded from a server, it’s very easy to forget how much psychological impact physical objects can have.
Data exists in some ether that your mind never really has to deal with completely. Physical things have presence. They take up space. They can arrest your vision. When you move them they stay moved. You can fold, spindle and mutilate them as you wish.