Final answer:
In advertising, the bandwagon propaganda device claims that everyone is using a product to encourage others to follow suit, as a way of belonging to the majority.
Step-by-step explanation:
Advertisers claiming that everyone is using their product is known as the bandwagon propaganda device. This tactic exploits the bandwagon fallacy by suggesting that since many people are doing something, you should too, in order not to be left out. The idea is to create a sense of popularity and social pressure, implying that buying the product will help you fit in with the majority.
In advertising, this is a common strategy to increase sales by leveraging the human desire for social conformity. For example, an advertisement might show large groups of people using a product and enjoying themselves, suggesting that this is the norm and encouraging viewers to join in. The message here is clear: "Don't be the only one left out; use what everyone else is using!"