It doesn't take too much common sense to figure out how over-breeding of a certain breed of dog happens. Popularity, usefulness, and sometimes even fashion, along with other factors, can lead to a breed having too many pups for how many people who actually have the ability to care for them. Puppy mills, caring only for profit and nothing for the health, security, or stability of the dogs they breed, create the plethora of popular puppies to help appease the demand.
But does the Black Russian Terrier fall into this category? Research shows most reputable, independent experts, including the American Kennel Club, believe that there isn't an excess of demand for this dog, originally bred to be a military guard for the Soviet Red Army. It easily has the capacity to be a fine family dog, the Black Russian Terrier is quite useful at working as a guard, competing in agility contests and fulfilling the role as a therapy dog. But without a famed movie, book, or television program pushing its popularity, there aren't many red flags being raised by experts.
There are reports of people doing independent research finding that every breeder they've talked to have yet to find a Black Russian Terrier that has as stable temperament. This again goes against the most common opinion that the breed is a loving, playful dog, as long as it is properly socialized while its intelligence and work ethic is challenged and stoked. The breeders in this study did seem to chalk up the temperament problems with owners who did not dedicate the time and energy it takes to form a well mannered Black Russian Terrier.
There is also a bit of misinformation in this argument, as the other major point is that the Black Russian Terrier is a "recent creation" and that there are plenty of other breeds that can fulfill the role of the working class dog. This does not take into account the documented history of the breed, or the documented history of dogs in general in post-revolution and post-war Russia. Dogs of all kinds, especially purebred dogs, were a rarity in this historical period in Russia as they were slaughtered in great numbers. The Black Russian Terrier was bred to fulfill a specific need: A dog to use in national security, at boarder crossings, military bases and prisons. This is ignoring, of course, the oppression these dogs were used for in the Cold War period of Russia, but the fact remains that there were no working class dogs that were readily available to the Soviet bloc countries.
The Black Russian Terrier is not being actively bred down from its original counterparts. It is a fully recognized dog in the United States and internationally, and therefore should not be considered a recent manufacture. When the dog was finally released to private breeders, it was they who helped the dog become a loving, even-tempered member of society.
The Black Russian Terrier is perhaps finding popularity because of its recent inclusion as a fully recognized breed by the American Kennel Club in 2001. But this type of popularity should not be confused with overbreeding.