a smart is not a normal car. it is more computer than car. the ignition switch doesn't really control the ignition, or even the power to the car. it is a switch that gives the computers an input as to what you want to do.
You will notice that when you start the car, you turn the ey and release it right away, the car still cranks and starts. Same when you shut it off. There have been times when I get in a hurry and park, put it in park and shut off the key rather quickly. The car will then start beeping at me. First time it happened I freaked out a bit but I found that turning on the key again, waiting a few seconds and turning it off would silence the beeping. it also would eventually stop beeping too.
It is just your car's way of reminding you to slow down and take a breath once and awhile.
