> Often you want to use interrupts instead of polling - well again, you can just ignore subsequent interrupts if they are within too short of an interval.

And you are really screwed if you have to do it with an extremely simple, and cheap IC, like 4 bit micros, because their CPU power may well be not enough for that, especially if they are to control something real time.

This is exactly why super cheap electronics uses conductive rubber buttons. Conductive rubber buttons don't bounce.