Yeah, I've seen the Mr. Haneys of the chicken world. Not pretty!
NPIP is fairly meaningless. NPIP breeders are just as responsible for spreading disease as anyone else by selling carrier birds. The reason I don't buy started birds and all are hatched here is so I can be a reliable source for other people. I must keep my flock as healthy as possible, which means proper management and keeping strong immune systems so if something passes through, they are strong enough not to be infected in the first place. It's really all anyone can do. Nothing is foolproof because no one can see a germ.
What you need to watch out for are the folks who treat their birds' "colds". No such thing. I once asked a guy if he'd heard of any diseases in our area floating around, as sort of a test. His answer? "No, I just see the usual crud and treat with antibiotics". Well, I would not buy from him! Stay away from those types. I just stay away from everyone, even those I trust. Even if they think their flock is healthy, they can't see germs, either, and if the birds were infected with something just prior to me purchasing the bird and symptoms showed up at my place, my flocks might become infected with whatever it is. Doesn't mean the person was lying, necessarily, though I've watched a lot of folks try to sell what I knew to be carrier birds. Not cool, people, not cool.
I agree with Mr. Cynical. I'm your long-lost cousin, I think. Good point, no one shows their certificate and if they post their number, how many actually check it out? Plus, seems to me that the testers themselves going from farm to farm might be responsible for spreading stuff if they become lax in their sanitation practices. I know one tester for GA, a man I highly respect. I hatched eggs he sent me six years ago. He's been breeding chickens bout as long as I've been alive....and that's a stretch more than 25 years, I can say. He got a breeding rooster direct from a famous breeder out west who has kept up a spectacular line of Plymouth Rocks for over 50 years. Before he would [put the rooster with the hens and before he would even send me eggs, he put that rooster through the usual tests, plus every other test he could come up with and gave him a clean bill of health. It's folks like that I will buy hatching eggs from when I need them, which isn't that often, thankfully.