Okay, case in point - someone bought two bitches and a dog of my breed, bred the dog to the two bitches (closely related) and sold them to Harrods, who were selling them at £600 when the going rate for the breed was about £250. Our breed club wrote and asked if the parents or puppies had been eye tested, and whether the new owners were being told about the serious eye problem in our breed which reputable breeders were trying to breed out, whilst waiting for a DNA test. They agreed they knew nothing of this, and would not be having the breed again. It turned out the parents of these puppies were carriers, and so by the law of averages some of the puppies would have been affected. As they don't get this till they are up to four or five years old, they could have been bred on from, thus perpetuating the condition.
Even the RSPCA says puppies should be seen with their mothers, and selling them in pet shops or on the internet leaves them open to all sorts of problems with infections, lack of socialisation etc, and is why people come on here asking for help when they get a problem.