Advertising is product promotion and marketing. One way to market a product is by subliminal association of products with well-known identities like celebrities, sporting greats, smiling people and sexual imagery. Advertising can be very pervasive and can take many forms such as audio, graphical billboard, web page or magazine advertisement, before video recordings, at the movie box office, etc
Because of wide-scale marketing that only interests a small percentage of the populace, the majority of advertisement-based media delivers information that is useless and often annoying, especially noisy. On the Web, Banner Ads, Pop-Ups, and Spam are all annoyances that can be adjusted.
While ads pays for a wide variety of commercial and public television shows, sports events, and more, there is no requirement to be a captive audience. Advertising can be moderated in various ways. An interesting article on ad reduction / blocking, in this case with the Tivo product on Slashdot.