I liked the story about the guy whose car got moved while he was in Home Depot, but not surprised.
We have had several Dodge minivans. Believe it or not, the keys for our last two, a 1997 and a 2001, were almost interchangable. The '01 keys always worked in the '97, and the '97 keys would usually work with the '01.
This gave me an idea for shopping for a new car. Always try your old keys in the new car. If they fit, you can save wear and tear on your pocket and your ignition. You could even try just driving the new car away. When you get pulled over, you could simply explain that the key fit, so you thought it was your car. You might be able to test drive the new car for a few weeks before they track you down.
Something similar, myself and a friend were shopping (using his car for transportation). Well we got done,went to the parking lot and got in the car, he put the key in the ignition and it would not turn. Well it turned out we were in the wrong car (looked exactly the same as his).
I had a rental car that was identical to a colleague’s rental. I opened the door with my key, but it would not start the car. I finally got out, looked at the license plate and discovered the error.