First thing that comes to mind is, are these scanners safe – i.e., do they have any kind of active radio wave source? How reliable are they? Can they malfunction and emit harmful radiation? Is it health certified for kids, adults and pets? What about medical safety devices? Is there a stringent regulatory body certifying these?

Second, how does law enforcement of the normal kind work in a society vs how does terrorism prevention work? For the later, intelligence gathering/sourcing, infiltration etc. - isn't this the only realistic (scalable) way for it work? If terror prevention becomes part of law enforcement job, then we will end up with a police state that is unlivable (in effect, terror is now perpetrated by state!)

Now, is this scanner device to be installed in public places – is it for law enforcement or for terror prevention? If the day-to-day life habits require this level of monitoring for law enforcement, then that society is screwed up beyond repair.

Btw, in my country we have X-ray for bags and metal scanner for body in every hotel, mall, theater, public transport hub, offices etc. There's usually a security guard who will wave a wand on your body but doesn't really know how to use it. For vehicles they make you open the trunk and boot and visually inspect as well as look underneath with a mirror. But I have not seen any 'positive' (false or otherwise) catch.

In movie theaters, the best I have seen them catch and confiscate is outside food (for commercial policy reasons, not security) and cigarette lighters (for fire safety and smoking ban).

It was irritating at first, but now everyone has become numb to it and you just go through the motions.