I've used it to implement job security. In some of my more complex classes -- ones I'm sure no one else can understand because they have methods with hundreds of lines and cryptic variables like x and cj -- I will occassionally look up the calling class's name. If it's a class written by a coworker that I don't particularly like, I'll pick a random number and return a incorrect result 1 out of 10 times.
This is just often enough to cause them heartache but not so frequent that they realize what's really going on. Most times they quit out of frustration, but even better if they're "let go" for incompetency.
Wait a minute, none of you know my coworkers, do you?
Just to be safe . . . For the humor impared,
this is a joke.