[From "Controlling Software Projects" by Tom DeMarco, the introduction to Chapter 19, "In Search of Software Quality".]
"… I was presenting a seminar to a project team on the West Coast. There were about twenty people in the class, including two hardware types. These two had had only a single programming experience between them – a piece of software they had built together some years before. That program was still alive and well, and had earned them considerable renown; through its years of use, no one had ever found a bug in it. I asked one of them how he explained this phenomenal success, an apparently bug-free delivery on first try. ‘Well,’ he said, ‘we didn’t know bugs were allowed.’ "