Andrew Garcia Philips and Sarah Slobin (plus five data gatherers) of The Wall Street Journal report on the prevalence of trackers and cookies on the fifty most popular U.S. websites:
Marketers are spying on Internet users — observing and remembering people's clicks, and building and selling detailed dossiers of their activities and interests. The Wall Street Journal's What They Know series documents the new, cutting-edge uses of this Internet-tracking technology. The Journal analyzed the tracking files installed on people's computers by the 50 most popular U.S. websites, plus WSJ.com.
Websites (top half) and tracking companies (bottom half) are placed in the circular network diagram. Roll over a website, and lines flare out to the tracking companies that collect data about you on that site. Similarly, roll over a tracking company to see what sites they sit on. Lines are color-coded to indicate first-party tracker files and third-party ones.
There's some clean, well-thought design and detailed reporting going on here by WSJ. You almost expect a piece this hefty to be clunky in the interaction, but everything works as expected. Take a look at the interactive (or the methodology) for yourself. There's a lot going on and interesting tidbits to explore.
How do you feel about all these companies collecting data about you, what you're browsing, and what you click on? I personally am okay with it - as long as it's anonymized and improves my browsing experience (i.e. ads that are relevant to me).