"The system uses millimeter waves, which can penetrate only 1/64th of an inch of skin, just enough to cause discomfort. By comparison, common kitchen microwaves penetrate several inches of skin."
So even really thick-skinned folk need to keep away from the microwave oven. Good to know.
Aside from that, millimeter waves are not in the light range, but just below infrared in frequency. Similar systems are also being developed for airport security as well. Consider the penetration of clothing, but not flesh, to see what is being carried on the person. Superman's "xray vision" may not be far away. But I don't know many who would like being observed naked by security personnel.
Energy falls off proportional to the square of the range. What's more, a medieval-type shield made of metal (or some other dense material) may be a simple & effective countermeasure here, for the same reason you can't put metal in a microwave oven.
Those who will not govern themselves must needs be governed by others.
Imagine if they can install these in a satellite and use it to straighten out everybody who is out of line...no more police needed, no prisons, just put every convict into the sights of this toaster gun, and they'll be sure to stay out of trouble. Next, incorporate the use of cell phone technology, and in an instant, any citizen can call in the coordinates and zap their fellow citizen who they are upset with...straight down from a satellite. Late on that credit card payment, or mortgage? well the banking systems now have a way to make you compliant real fast. A home model can be used to start the fireplace, no matches needed any more...even cook the roast faster than that microwave ever did. Is that dog not staying in the yard? No "fence" needed, just put on a tracking collar that focuses this gun, and Spot will be in line from now on. Is the neighbor's dog in your yard? Well...it was "sunburn" right? The super sized model of this thing can do a whole country all at once...if they step out of line, EVERYBODY gets cooked until they give up. Where will all this end?