It's one of the biggest fads nowadays. Breeders come up with stories about "hybrid vigor." Theoretically, because most diseases have a recessive link, and you're more likely to pick up on that with a common ancestor, a purebred would be more at risk because it could have that same ancestor in the pedigree -- HOWEVER -- what most people don't realise is that the extreme majority of purebred dogs are not in any way related to eachother for many many generations, and thus can be just as at risk to one disease as mixed breeds are, and not only that, but you are combining the poor genes of one breed to the poor genes of another. Unpredictablity comes in all sorts when breeding mixed breeds, which is one reason there are more mixed breeds in shelters than purebreds -- backyard breeders tell tales about how your goldendoodle will be non-shedding with the coat of a standard poodle -- but when it's 6 months old and it's adult coat is coming in and you realise this is a shedding golden coat, not a non-shedding poodle coat, where does it end up? People say your "labweiller" will look mean like a rottie but have the sweet temperament of a lab, and when you realise it not only look like a rottie but has the temperament of on as well, where does it end up? Today's society is not able to deal with unpredictability. If people want a mixed breed they should go to a shelter or rescue!!