I was taking an introductory programming course. One assignment was to do a little payroll program, including some data validation. The program was supposed to accept terminal input and send output back to either the console or a printer.

Suddenly the printer began spewing out paper like crazy. One of the students (a particularly mouthy woman) had programmed a less-than-helpful error message ("YOU ARE WRONG") and then not provided any exit from the error-checking logic -- the program just re-read the last (failing) input and re-tested it. All in all, it was a very nice infinite loop.

After spitting through about fifty pages of "YOU ARE WRONG," somebody cut power to the printer, and the instructor had to flush the print queue manually. He went back to the student and asked if she had tested the program by sending the output to the console before trying to print it, and she said, yes, she had tested it on the console and ended up with a screen full of "YOU ARE WRONG" messages. Why, then, had she sent her output to the printer? "I thought I would be daring!"