I don't think a breeder would consider a BYB if it has good lines and got their breeding dogs from reputable show breeders. This breeder should also know and study all the dogs in that dog's pedigree. They should be able to know the faults and the good qualities of most of the past dogs. That's why it's good to get a dog from a reputable breeder. A breeder should always be looking for show prospects in puppies when breeding. Even if the breeder doesn't like showing, they should be willing to get that pup shown with a professional handler. So if you want to breed, get dogs from reputable breeders, and buy the breeding rights. Note: if that breeder thinks that dog should be sold as a pet, there should be a good reason.
Most BYBs are linked to puppymills unfortunately. A BYB in my opinion, is just someone who wants to breed two pet quality dogs together because they either want money for the puppies or they think puppies are cute(which they are, but there should be a better reason for breeding). Most of these dogs are from the pet shop, because a reputable sells their pet qualities with limited registration, therefore those dogs are not supposed get bred. This insures that their lines are protected and it is keeping the breed pure from inherited problems. It's where they get their breeding stock that really matters to me. Most are from other BYBs or pet shops which originally they came from puppymills. BYBs and pet shops don't care if you breed the dogs, and then that person will breed, then the next person, and the cycle keeps continuing.
I don't know of a BYB that sells their dogs on limited registration but maybe some do.
Just my 2 cents.
