As with anything, you have breeders that are good, some that aren't.

In general, breeding is good. Its a good way to preserve a specific breed or try for certain traits. Bad breeding is done by some people that breed only for money, breeding dogs, cats, or any animal to sell them to turn a profit.

We helped with a transport last year of two deaf great danes, the breeder was so set on profit (or she was just not that smart), she was breeding brother and sister. She kept wondering why many of the puppies turned up deaf.