Honestly, many people do not know about this piece of information. Since free mobile app are available everywhere in the app store. Do you think of the reason why someone would spend thousands of dollar to give away free app? What or rather how do they make money from? Answer: Your data. See this infographic below. Having consumer data will allow companies to do retargeting and remarketing. The profit is huge once you know when your customer will be online, what they buy, where they stay and what is their buying pattern. Which lead me to understand why Facebook never charge you for using their app.