Some people say that what you put on the internet never goes away. Perhaps it's just a cautious way of thinking about what you upload, but in reality, things really do fade away. And if a particular datum isn't ever completely eradicated in your lifetime, it gets diluted among the huge amount of data that get uploaded everyday.
It was on this theme that I created Fade Away 1 for my Introduction to Physical Computing final. It performs a twitter search for the term "fade away" and uses an ultra violet laser diode to write these tweets on a phosphorescent surface. Each character has been programmed into an Arduino, which controls the servo motors and the laser.
More information here: http://mattrichardson.com/Fade-Away/