I'm a bit disturbed by the frequent insistence that any particular Mad Cow is not a danger to the public "because it never entered the food chain." To me that's a little like telling your parents that the broken window couldn't be from your rock, because you still have a rock in your hand.
See, USDA, it's not that specific cow that is so worrisome--it's all its cohorts that did make it into the food chain.
In one of those links above, I was especially repulsed by the discussion of "restaurant plate waste" being a vector for giving cows BSE. It's gross enough that "restaurant plate waste" is being fed to herbivores in the first place.
But on consideration, I realized that what should disturb me a lot more than that is: people were eating whatever was on those plates before the cows were! And as we all know, prions never die.
Of course, if we were all vegetarians (or even just carnivorous hunters), this wouldn't even be a concern.