I was thinking along the same lines. If, for instance, a car is stopped on top of the bag in traffic, or at a red light, then I imagine accelerating while on the bag could cause potential ripping, or depending on how deep the hole is, it could pull the bag right out, leaving it as a hazard for other cars. Not to completely discount this idea though, because I do think it's quite innovative.

Not just park, I'm guessing it'd take a few seconds of rest for your wheel to sink in it. I guess it'd probably rip the bag and sink in the hole completely.

Nyah, I guess that the reason they went for tough kevlar bags is to be able to withstand the weight of the care. I think it would sink a bit but cause any damage or pose a hazard to the car.