"Since the speed that people swipe is going to be variable, it can't be too hard to read a card without knowing the speed." The speed just has to be fairly con

"Since the speed that people swipe is going to be variable, it can't be too hard to read a card without knowing the speed." The speed just has to be fairly constant within a single swipe - then you can adjust for it. It usually is when humans do that - human hand has quite an inertia. The security feature on ATMs makes it vary wildly within a single swipe.