I'm Being Followed: How Google—and 104 Other Companies—Track Me on the Web
"There's nothing necessarily sinister about this subterranean data exchange: This is, after all, the advertising ecosystem that supports free online content. All the data lets advertisers tune their ads, and the rest of the information logging lets them measure how well things are actually working. And I do not mean to pick on The New York Times. While visiting The Huffington Post or The Atlantic or Business Insider, the same process happens to a greater or lesser degree. Every move you make on the Internet is worth some tiny amount to someone, and a panoply of companies want to make sure that no step along your Internet journey goes unmonetized."