Matt, I liked your post. It provides some perspective for what we do in the dojo. I read a study in Black Belt magazine that analyzed knife attacks. It may be the same one mentioned above that studied 250 attacks in Baltimore.
One of the surprising (to me, anyway) observations in the study was that the majority of fatal attacks were "ice pick" attacks to the back of the neck or upper back. This is a lot like a shomen uchi attack.
Back to the question at hand, we do most of our takeaways after the pin, but we sometimes have techniques where the knife comes out during the throw. We almost
never knock the knife out of our uke's hand because (1) a flying knife is unpredictable, and (2) it's not really tanto tori if you don't tori the tanto.
Regarding the larger issue of knife defense, I'd prefer to have pepper spray or a firearm handy if threatened by a knife. That way I can counter a contact weapon with a distance weapon.