The new LiPo cells for car racing that I have seen are all cased in hard plastic that seems to give the cells more protection. If you crash hard enough to break the case then you definatley want to check to make sure the cells were not damaged. I have not seen any damaged cells at any of our local tracks and I have seem some pretty big crashes.
I watched one car with a LiPo pack get airborne off a corner dot and fly into a concrete wall. He damaged the car pretty well but the pack was in perfect shape.