If you find yourself using Apple's private key (or private "anything") this should be a clear signal that your innovative energy should probably be spent elsewhere - seems like common sense to me.
Also, if you start trying to convince yourself that your app does not violate the guidelines because there are other apps do what you want to do, even though your intuition tells you that your app will be rejected, spend your energy elsewhere. Apple has no concept of "precedent" in making their decisions (nor should they or could they), and they make clear that the existence of another app doing what you do is not the basis for a successful appeal.
I'm not saying don't push the boundaries of the guidelines, but if you do so, understand it to be a business risk. And if Apple turns around and rejects your app, accept it as a cost of doing business on the edge, and don't act like Apple is to blame for the risk you took and take your sense of persecution public.
AirPlay is a strategic technology for Apple - it is going to become more and more important in the next year. Any moves Apple makes to protect this technology are first and foremost going to be motivated by ensuring the best, most consistent possible experience for the end user - their interests rest with the whole device ecology and how those devices interact. The motivation is not crushing third-party implementations because they don't want to compete with them or because they want licensing fees (which are trivial to them) - it is because they don't want hacked implementations screwing up the end-user experience, especially for non-geeks.
Also, if you start trying to convince yourself that your app does not violate the guidelines because there are other apps do what you want to do, even though your intuition tells you that your app will be rejected, spend your energy elsewhere. Apple has no concept of "precedent" in making their decisions (nor should they or could they), and they make clear that the existence of another app doing what you do is not the basis for a successful appeal.
I'm not saying don't push the boundaries of the guidelines, but if you do so, understand it to be a business risk. And if Apple turns around and rejects your app, accept it as a cost of doing business on the edge, and don't act like Apple is to blame for the risk you took and take your sense of persecution public.
AirPlay is a strategic technology for Apple - it is going to become more and more important in the next year. Any moves Apple makes to protect this technology are first and foremost going to be motivated by ensuring the best, most consistent possible experience for the end user - their interests rest with the whole device ecology and how those devices interact. The motivation is not crushing third-party implementations because they don't want to compete with them or because they want licensing fees (which are trivial to them) - it is because they don't want hacked implementations screwing up the end-user experience, especially for non-geeks.