Cory Doctorow is not surprised:
In part, this is because the TSA is staffed by clods and jobsworths who are capable of maintaining the solemn pretense that breast milk and nail files are existential threats to the aviation system.
They always look bored, hostile or both, to me.
Much more important is the fact that it is neurologically impossible to remain vigilant for things that never happen. If you ask yourself to maintain vigilance for incidences of common water bottles (which your adversaries persistently try to smuggle past you, both deliberately and accidentally) and incredibly rare, nearly unheard-of, statistical outliers of weapons and bombs and such, your brain will get very good at recognizing water bottles, largely by de-tasking and commandeering the neural stuff that's meant to be looking for AKs and plastique.