There is nothing more evil in modern business than marketers. Between real life experience and MBA classes I have come to despise most everything involved in modern marketing, especially in the technology space.
Give me a break. This isn't evil marketers hiding in their underground lair. This is web developers, designers, and product managers gaining insight about their users. They don't package this information and sell it wholesale to advertisers. They use it to make the product better . You are taking this -way- too seriously. The ability to have perfect information on how users interact with your product is one the earth…
It's used to allow publishers to make more money from their consumers through advertising.