The data economy powered by Chrome extensions is pretty vibrant.
Popular Google Chrome extensions are constantly tracking you per default, making it very difficult or impossible for you to opt-out. These extensions will receive your complete browsing history, all your cookies, your secret access-tokens used for authentication (i.e., Facebook Connect) and shared links from sites such as Dropbox and Google Drive. The third-party services in use are hiding their tracking by all means possible, combined with terrible privacy policies hidden inside the Chrome Web Store.The Detectify team has identified how they are doing it and what options you have to avoid being affected by it.
Source: Detectify Labs