They bank on the general public not being able to reason logically. Take this hypothetical scenario, for instance:
My small isolated, closed flock of less than 30 chickens is five miles down the road from the commercial chicken farmer with his meat/layer birds housed in the long metal building with huge sliding doors on each end. Said farmer opens the door and in flies a wild bird, loaded with whatever virus he's carrying, and infects a couple of the chickens. Because of the cramped quarters/monoculture of his warehouse operation, said virus travels like wildfire through his bird population. Where is the wild bird who started it all? Dead among his chickens or flying off on its way to South America, if it gets that far. What's the likelihood that that one bird will come in contact with my little flock? Almost nil. What do the Feds do when they get wind of the infected flock? They cull all flocks within a pre-mapped Kill Zone without testing. What do they succeed in doing? Wiping out a bunch of healthy HERITAGE breed chickens for no reason whatsoever. Under NAIS, they are not required to test to see if my birds are infected nor do they have to get a warrant since NAIS is under Homeland Security and no one under the Homeland Security system really has any rights anymore.
How in this case, has my premises being registered with NAIS helped to stop the spread of disease? It hasnt and it can't. It can't. It will however, limit the gene pool and wipe out more of our already endangered heritage breeds. I bet the commercial farmer will have his flock replaced by some gov't subsidy or something. They're just a commidity to him anyway; but will they replace mine? Of course, they wont. And they can't really replace my pets, my girls who each have a personality and I care for deeply, that I raised from day old chicks or that I hatched in my own house.