One of the many Tricks of the Propagandist, this propaganda technique is highly effective because it preys on the very basic psychological human need to "belong to something" and "fit in with the crowd." The method is simple. Once the product you sell has reached a point where it is reasonably "popular," use that fact to your advantage, as a selling point. "Choosy moms choose Jiftm" is one example. By telling people that a large number of other people have decided to purchase your product, you convince many of them to believe that your product is superior. We'd like to think that this is because everybody else had the good sense to identify and purchase a worthy product, but we are only fooling ourselves. I think this is merely a rationalization, an exercise by the pseudo-logical mind to explain away an emotional, foolish decision. The emotional urge to feel "normal" is far stronger than the pseudo-logical urge to "buy something that must be good because everyone else has it."
The "argument" that something is better because many people buy it is fallacious, for the exact same reason that the argument that a statement is more true because more people believe it is fallacious (<cough> "95% of the population believes in God, so there!" </cough>). Companies know full well that sales are no indication of product superiority, but of marketing ability and brand name acceptance. McDonald'stm is a perfect example. They claim to make the "best fries in America" (based on sales), when in fact any discriminating person can find far better sources of fried potatoey goodness just about anywhere. Personally, I find frozen "waffle cut" or "fajita fries" bought at the supermarket to be superior to what McDonald's has to offer.
The fallacy of claiming superiority based on wide acceptance is known as "argumentum ad numerum," and the fact that bandwagon propaganda is so effective despite its fallacious nature is a sad assessment of the logical capacity of our country. In essense, we let our emotions get the better of us in our constant effort to conform to what's "normal," to feel as if we have a sound "place" and identity in society. This is ironic, considering the end result is total conformity and a loss of identity.
While everyone tends to blame the big businesses for the degeneration of society into little more than a pissing contest to prove who has the most acceptable clothing and lifestyle, the homogenization of the American dream is our own undoing. Our own competitive drive to be better than everybody makes us ultimately powerless and indistinguishable. I truly believe that bandwagon marketing works most effectively on children, meaning that parents are most at fault for improperly arming their children against the onslaught of commercialism. Rather than give children some perspective as to why they're being told by the nice TV voice they absolutely must buy such-and-such Pokemontm merchandise, we plop them in front of the TV and let their simple minds wander unsupervised, fending for themselves against memes that have been carefully crafted by experienced marketing executies. Television continually reinforces the notion of acceptance and conformity, a message that hits home well with kids, who must live and struggle in a societal microcosm called "school" where they may be bullied and harassed for straying from the herd.
After being conditioned into this lifestyle of fearfully changing one's identity to match that of others, we can only expect hapless children to grow up into mentally defenseless adults, ill-equipped to cover their ears and defy the orders of their corporate gods. Personally, I have long been cynical towards advertising, and find that being assaulted by commercials often enrages me, as I can almost feel the slimy memes trying to infect and infest my brain. I can thank my sixth grade teacher for helping to provide me with this attitude, as we were required to do a school project on propaganda and identify specific examples of the many techniques outlined in Tricks of the Propagandist. Kids aren't fundamentally stupid, but they are naïve and will not immediately understand the intentions of those behind the commercials they watch. Perhaps if we educated them to be more savvy and less gullible... It's not going to happen in school, considering how much of the public school system's income comes from Coketm or Pepsitm.