After the story about Target discovering a woman was pregnant and made the information public, a college professor decided to try and hide her pregnancy from "big data" to keep it private. She did everything she could to be private, including routing her online traffic through Tor (an anonymity network), using an alternate Amazon account, and having items shipped to an alternate location. She also quit using Google in favor of the Duck Duck Go. She found that as long as you're on the internet, it's incredibly inconvenient and impractical to effectively keep yourself private while using these services.
Leo says that not only does Google see your activity and target you with ads, but your internet service provider sees everything you do as well.