A frequent misconception of Do Not Track is that the goal is to prevent tracking by online advertisers. In fact, tracking is a much broader problem on the web, and our Do Not Track vision at Stanford, while principally aimed at "third-party" tracking, does not focus on specific industry segments. Barocas and Nissenbaum said it best:
It is important to note that OBA [Online Behavioral Advertising] has borne the brunt of what might actually be a wider debate about the monitoring of user activity online, and even more widely, the aggregation of personal information for a variety of purposes. Because OBA has a public face in the form of ads, it attracts more attention than the less obviously visible user tracking that is essential to the business of research and analytic companies and certain content delivery firms. That said, the outcome of OBA regulatory efforts could have profound consequences on what counts as legitimate practice in online monitoring and beyond.
What are some examples of third-party tracking not directly related to behavioral advertising? The Facebook "like" button is a prominent one — Facebook can keep track of all the pages you visit that incorporate the button, whether or not you click it. Did you know, for example, that the UK National Health Services website has the like button, among other trackers, on all their disease pages?
Trackers whose presence is visually apparent on the pages they track are worrisome enough, but there are many, many more tracking-enabled embedded objects that are hidden from view, such as analytics. Popular websites incorporate on average 64 trackers on their pages. There is no question that consumers do not expect this.
Business models on the web evolve almost as fast as the technology itself. Five years ago, behavioral advertising was almost unheard of; who can predict what tracking will be used for five years from now? That is why it would be a huge mistake to focus the Do Not Track debate on behavioral advertising alone. That is also the reason why even if the NAI somehow got its act together and made its opt-out tool work perfectly — not that it's likely — it would not diminish the need for a Do Not Track mechanism in the slightest.