Introducing Anonymous Login and an Updated Facebook Login
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.