You invent a new product, and sell it out of a shiny apple-store-style emporium. Trendy! Now the naturre of this product is that once a customer buys one, s/he instantly loses the ability to make rational judgments about what is best for him/herself; also becoming disinhibited, happier, stupider and more suggestible. It won't take much for you to sell him/her a great many more of your products.
Ladies and gentlemen: the pub.