Originally Posted by RRDD

Your cab driver is using a variation of the mathematical consequence of "large numbers". Here are a few variations of the "trick":

1. A guy goes around to various towns in a drought stricken area and claims he can make it rain by beating on his drum. He even tells the town that they only have to pay if it actually rains. The guy then beats his drum. If it doesn't rain he leaves. If it does rain, he gets paid.