Someone needs write a history of advertising. Something that pulls together how influential companies have marketed products over the years. It’d probably show quite clearly how culture follows advertising, not the other way around. Plus it would explain how advertising works, because most people have no idea.
Take the annoying “sex sells” quip. First, subliminal messages don't work. Secondly, few people know what “sex sells” actually means. You can't simply put the word SEX or some phallic-shaped object in an arbitrary image and expect the audience to assume the product has a sexual context. You could print the word sex as large type on a gigantic billboard, and it wouldn't work to invoke sex in the minds of viewers.
Advertising uses sex to manipulate on the symbolic level. It works by connecting the product to an unattainable sex object, creating a gap. The woman is beautiful, but you can never get her. She is holding a camera, which becomes a desirable object simply because the desirable female sex object holds it. But in contrast to her, the camera is attainable. Through this process, the object which is desired by the viewer’s sex drive shifts from the woman to the camera, and the camera becomes a sex object in her place. Simultaneously, within the image of the ad, the woman’s gaze is fixed upon the camera, so it is represented as her object of desire, convincing you – the viewer/consumer – that because she desires the camera, your possession of it will attract her to you. Simple.
It’s important to note here that there’s no logical reason to sell a camera by showing a beautiful woman holding one. It tells you nothing important about the camera’s function, or why this particular camera is better than other cameras. It only works because the viewer/consumer is presumed to have a sex drive. Sex in advertising works by sending messages to this psychological apparatus. Not by trying to hide the word “SEX” in the image.
Also, this operation is so fleeting that it doesn't last long. You don't look at a camera ad and then forever think that if you buy the camera you get sex with that girl. At best, it leaves the lingering sense that this camera feels/looks/is sexier than the others. One of the most insightful parts of Freud's theories is that we don't necessarily want the object. We just want the wanting.