google

“Seeing ads next to your e-mail (if you use Google’s free e-mail service) can provide reminders, sometimes startling, of how much the company knows about your inner self. Even without your e-mail, your search history reveals plenty—as Levy says, “your health problems, your commercial interests, your hobbies, and your dreams.” Your response to advertising reveals even more, and with its advertising programs Google began tracking the behavior of individual users from one Internet site to the next. They observe our every click (where they can) and they measure in milliseconds how long it takes us to decide. If they didn’t, their results wouldn’t be so uncannily effective.”

—	James Gleick, author of the superb The Information: A History, A Theory, A Flood, on how Google dominates us