Ontrack, which handles data recovery, compiled a list of the strangest reasons data was lost. You can read their list here. I remember when I was teaching TSM some students had some of the craziest stories for data loss (many were disgruntled employee stories).
One story I heard from a student occurred when a manager was stupid enough to fire an employee, but require him to work the rest of the week if he wanted his pay. So the employee worked the rest of the week and on his way out (unescorted) he went into the server room and proceeded to urinate into the mainframe. Supposedly he shorted out the mainframe and caused all kind of havoc. If you have a story you'd like to share feel free to leave it in the comments section.