3. What would happen if there were no behavioral tracking on the Internet? Ever get the feeling somebody is trailing you on the Web, watching your every click? Do you wonder why you start seeing display ads and pop-ups just after you’ve been searching the Web for a car, a dress, or cosmetic product? Well, you’re right: your behavior is being tracked, and you are being targeted on the Web as you move from site to site in order to expose you to certain “targeted” ads. It’s Big Data’s dark side.

Individual Web sites and companies whose business is identifying and tracking Internet users for advertisers and marketers are collecting data on your every online move. Google, which handles more than 3.5 billion Web searches each day, knows more about you than your mother does. Many of the tracking tools gather incredibly personal information such as age, gender, race, income, marital status, health concerns (health topics you search on), TV shows and movies viewed, magazines and newspapers read, and books purchased. A $31 billion dollar online ad industry is driving this intense data collection.

Facebook, which maintains detailed data on over 1 billion users, employs its Like button to follow users around the Web even if you log off. Its social networking site is one giant tracking system that remembers what you like, what your friends like, and whatever you reveal on your Wall. (See the chapter-

ending case study.) Plus, Google’s social networking tool, knows about your friendships on Gmail, the places you go on maps, and how you spend your time on the more than two million websites in Google’s ad network. It is able to gather this information even though relatively few people use Plus for their social network.