Kittens tend to ingest litter when first learning to use the box which can be very dangerous. I think this is why they discourage the use of clumping litter for kittens. I supposed cats can also ingest litter while grooming, etc.
I have heard of cats ingesting the litter and it being dangerous. I personally don't know of any cats that actually take bites of the litter, but I'm sure it has happened before.