I heard an iOS developer make a comment once saying that deciding to develop for iOS means less folks may have access (under the assumption that Android is more common) but you are guaranteeing that those with access to your application have more money to spend because of Apple's price point. If Facebook's targeting and ad exchanges are what productize the company's customers then I would say Apple does the same to a lesser degree by charging a premium for its exclusive ecosystem. I consider Apple many degrees safer because they heavily screen what can be added to the app store and the inherent nature of targeting going on is limited to "paid for an Apple device" instead of the greatly higher dimensional data accessed leveraged by Facebook.