I know that this topic is a sore spot for so many people. I recently bought what you guys call a "designer breed". Call me a horrible person or whatever...but she is what I wanted and I know that we would not have found her at a shelter (and we did look at shetlers before we fully commited to the breeder).
I think another thing that people are forgetting is that way back in the day, people would breed different mixes together to create a new breeds. They are the reason why we have so many different "purebreds" to chose from (I actually found this out when I was researching puppy information before we got our pup). I know that there are some breeders that don't care for their puppies...but there are also oweners who don't care either...they buy puppies because it is a fad, and they thought it would be cool to have one.
I can't remember who made the comment, I think it was several people, but most of those puppies and other animals are at the shelters because of neglectful oweners...not because of breeders. If you ever watch Animal Cops, you will see that is usually the case.
I would have loved to get a shelter dog (infact, we had two when I was growing up: 1 from the local shelter and the other was a stray that just walked into our yard). But your cirumstances make a difference as to what kind of dog you get. How bad would you feel if you got a shelter dog and you didn't have the time to give it all the attention it to undo the bad things that happened to it...I didn't have that kind of time to untrain bad things. That is why we bought a dog from a breeder.