If your business model is reliant on annoying the users of a proprietary 3rd party platform, you shouldn't be surprised when the rug gets yanked out from underneath you.
The point was that if Facebook are providing the APIs and encouraging developers to use them then it's a crappy thing to yank the rug away. I don't think that it's a great idea to build a business model that relies on Facebook - but at some stages of developing an app it is very useful to use Facebook facilities to implement a social graph and notifications, so that you don't have to.
They're willing (and smart) to leverage independent efforts where they assist this. But... only so long as they do.
Look at it from this perspective: If a functionality becomes important, would they not be "derelict" in their duty not to attempt to bring it under their control? In-house, acquisition, whatever.
If you choose to help them out, they're not going to say no. But you should keep the balance of power in such a relationship in mind.