Exposing frame zero is a phenomenon that happens a lot with rangefinders and older SLRs that do not have the auto load feature. Many times part of this frame has been exposed to direct light as the film was being threaded with the back of the camera open. Also many times, this frame tends to contain a good image. I find these frame zeros fascinating and enjoy discovering good ones, the blown out negative space adding to the image instead of destroying it.
Here is one from Tahrir Square in Cairo, shot on March 4th, 2011