Some of the "designer breeds" originally served a purpose. I believe the Labradoodle was one of them. It was one of the "oodle" breeds, anyway. It had something to do with people who needed service dogs, but had allergies or something. Apparently, the poodle's coat did not affect them, but the dog itself was not useful for that purpose. So they cross-bred them, and now the are used by people who couldn't use them before (I'm missing a lot of the story, but that's the just). That being said, I think there's more designer breeds out there for the wrong reasons, and I agree, that it is wrong to "design" a breed just for the sake of doing it.
Hagar:"What kind of dog is that?"
Man with dog:"He's a nice dog!"
Hagar:"You know, at the end of the day, that's always the best kind."