As this blog reported earlier - it is spooky when ads follow you around on the Internet. Imagine if you changed TV channels and ads followed you around the channels! Seen in this context the FTC 'do not track" proposal is really welcome. The consumer privacy at stake here is just huge as is the stake of the entire field of marketing research.
Marketing research in the consumer media behavior context tries to predict viewing behaviors based on samples and statistics. Statistics exists because you could not economically track media consumption behavior of the entire population in a target market. Let's say that you wanted to track the TV media behavior of all toothpaste buyers. In doing so a population study would involve recruiting and paying an entire "population" of all toothpaste buyers. Even covering a small geography of the market would involve huge expenditure- just to track the TV media behavior.
Now consder the same market and and how the Internet can now track visits to any dental, white teeth, oral hygeine and related websites. A toothpaste ad just follows consumers around the Internet as they go to a few toothpaste related websites and then anywhere else they go to on the web after they meet some initial qualifying criteria ( like visited 3 websites related to toothpaste in the last one week).
You really don't need marketing research and statistics over a random sample or paid panel because you are tracking the entire target market population- for free ! Market research and statistics are not as perfect as tracking software but they do protect consumer privacy.