Perhaps you've seen one of these before.
A couple of inches above and below the magnetic stripe reader are protrusions that allow just enough room to swipe a credit card. The barriers are a negative affordance (is that the right terminology?); they make swiping a credit card awkward.
I have to carefully place my card in the small space above the reader to start. After swiping I always end up jamming the card into the bottom barrier. If one wanted to apply Fitts's law to swiping a credit card, and intentionally violate it, this seems like a pretty good way to do so.
Yet, there must be a reason those barriers were added, and it doesn't appear to be structural.