Let's say you step into a cloning chamber. You push the button, and out you walk with your new clone!
Wait a minute... i came out of the wrong pod?!?!
If you go into a cloning chamber (you know, the cheesy soft scifi ones that instantly make a perfect copy of yourself with no loss of information or anything to build you out of), how do you know it's you that's going to walk out and not your clone? Will you be the original, or the clone? If you have the exact memories, exact appearance, exact mind, how could you tell if you were always the original you or if you're just a clone with you creator's memories?