You're an idiot if you implement this. On iOS, use the device token and implement truly anonymous login without having to deal with anyone else brokering your users' data; I'm not sure what the Android equivalent is, but it can't be much more difficult.<p>Remember, Facebook is the same company that cuts deals with shady data brokers like the Datalogix (the company that buys your grocery store discount card data and re-sells it, among other things) to build a comprehensive profile of everything you do. Using them for this pseudo-anonymous "anonymous login" helps them a lot more than it will ever help you, as a standalone developer.<p>I can't wait for Facebook to trademark the term "Anonymous Login," just to complete the irony. Remember, if it was actually anonymous, you wouldn't need Facebook's help to implement it.