I have been a paying member of the iPhone developer program for the past 1.5 years. I have not nor do I intend to write any iPhone apps. The only reason I have been paying that fee was to be able to add support for targeting the iPhoneOS in our compiler (http://www.freepascal.org) in a way that complies with Apple's licensing requirements.
Our compiler outputs straight ARM assembler code. It does not offer a generic middleware framework. Its run time library does not encapsulate the iPhoneOS (or any other platform) functionality any more than the standard C library does.
People using our compiler to develop iPhone apps currently develop their GUI in Objective-C. They use our compiler so they can reuse backend code from other apps they've written in Pascal, much like other people do with C or C++ code.
However, simply because the source language is called Pascal rather than C, I will be forbidden from working on it any further as soon as I accept the updated licensing agreement. I've not yet done that, and (presumably) as a result I've been locked out of the iPhone developer forums (and possibly other things as well).
I've been a Mac user since 1991, and for the very first time I am seriously tempted to abandon the Mac platform altogether, no matter how much I prefer using it to other systems. It just doesn't make sense as a tool developer to develop for a platform of which the controlling company may decide on a whim that you are no longer allowed to develop your tools for it (and at this point it would not surprise me if Mac OS X were to see similar restrictions in the future).
It is very doubtful that this decision would hurt Apple's business much and since you're making money hand over first (and since scores of Windows developers are hopping on the AppStore bandwagon anyway), I doubt you even care at all. I am however sad that I've apparently wasted the past 1.5 years and the associated €156 on the program, even more so that I wasted the time of the people that have used our compiler to create apps for the AppStore, and that you are completely locking down things this way.
While you are presumably trying to protect the platform, I believe that in the long term you will find that instead you are destroying it. I guess that whole round pegs in the square holes thing is really officially over...