Source: http://gizmodo.com/twitter-is-going-to-start-tracking-the-other-apps-on-yo-1663793680
Twitter is starting a new program called App Graph that tracks all of the other apps people have on their phones. You might be wondering why Twitter cares if you're a Candy Crush fiend or if you also use Instagram. It's because Twitter follows the ABT school of sales: Always Be Targetin'.