JMHO, but when breeds were hotly populatized by Disney and similar movies years back, we did not have the information that we do now, right at our fingertips. We also had good breeders that were not as aware of the issue, and overall did not screen buyers the same way, did not have limited registration contracts, etc. Breeders seem to be more organized now - five minutes after Uno won I was on the phone with my breed mentor and the subject of popularity & unfit buyers came up almost immediately. What I got a sense of in my breed, at least, was breeders banding together and erecting the proverbial brick wall with the influx of buyers that began flooding breeders with inquiries. I think there is such an awareness in the breeder's corner now, and moreover, many of the buyers that would have made impules buys now have resources on the internet & are making more informed decisions. There will always be impulse buyers and unscrupulous breeders who are ready to sell to them, but I think it's becoming less of an issue with purebred dog crazes stemming from movies or TV shows.
Just wanted to add that HSUS, ASPCA, & the like really have no involvement in the world of purebred dogs, and the more they stay out of our business, the better ...