Every other app that has done this in the past has been slapped down by Facebook for TOS violation.
As a general case, when you're building an app on someone else's platform, you absolutely must know the terms of service of that platform, otherwise you're just wasting your time (unless your goal is to learn the technology and APIs, and there's better ways to do that too!).
And watch out when the TOS changes and leaves you out in the cold. This is why it can be dangerous to build your business on someone else's business.
