Politics tells us that there will never be a "rule" that says that it's ok for Inkundernails and carolinaflyr to carry weapons on board because we were prescreened and found not to be a threat.

But good risk management can say "We know that carolinaflyer and inkundernails probably won't bring a Glock on board and we really don't care about their pocketknife, shave gel or shampoo so let's spend time and money on something , and bother someone, else.