I've been reading this with interest and wasn't going to chime in, but a few things have been said that I think are potentially dangerous for any "lurkers" reading this forum who are thinking about adding a cavalier to their home. I was one of those lurkers and learned a great deal by reading the information in the facts sections, but probably more from reading the stories and experiences of the cavalier owners on this board.
What Karlin said is probably the single most important thing for potential cavalier owners to understand -- WE, AS CONSUMERS, HOLD A TREMENDOUS AMOUNT OF POWER IN OUR HANDS. Whether it's cars or dogs, we can dictate what the "market" produces by limiting the demand for unhealthy cavaliers who do not possess the temperment and conformation for which this breed is so desired. It's very simple: if you desire a cavalier who looks like one, acts like one, and inherits the smallest chance possible for devastating health problems, then you must find a breeder who is equally concerned with breeding to produce such dogs.
This is entirely possible if you are patient and arm yourself with knowledge regarding what the recommended breeding protocols are. I live in the midwest, literally in the heart of puppymills and backyard breeders. I encountered several unsavory situations from which I walked away. I found a breeder, grilled her (as she did me) on cavalier issues, then waited almost 7 months for an available puppy. I know there are no guarantees, but my family is now blessed with a cavalier who bears the temperment of a loving pet and who (God willing) will face minimal health problems as her life progresses.
My puppy's breeder shows her dogs. This is her hobby, passion, and the only reason she breeds her girls. Supporting breeders who show their dogs is imperative in buying a puppy. I know my breeder didn't breed for the purpose of selling a puppy to me (or some other consumer). She did so in the hopes of producing that next "best in show" dog. In order to get that top dog she made sure that the puppies' ancestors had passed necessary health checks, were of sound temperment and conformation, and she carefully studied genetics and other elements to find the right breeding combination with a stud dog. I am the lucky recipient of a puppy who won't ever be "best in show," but she still bears fruit of my breeder's labor which hopefully means she has good odds in facing cavalier health problems.
It's just simply time for us to say enough is enough to these mill and byb types. It doesn't matter why the problems in the breed exist; what matters is that they do exist and we must use our knowledge and economic power to eliminate the demand for puppies born as the result of inadequate breeding practices.