Something's got to give
It's an aggressive and some might say greedy move by Apple to be sure. Even if the cut was 15% I'd wonder if they are overplaying their hand though. With Android growing at an incredible pace, the content providers and developers have much more power than they did a year ago and that swing looks set to continue. I'd be very surprised if more providers don't take a stand alongside Rhapsody.
Having said that, demanding 30% appears to be deliberately prohibitive and so perhaps they do just want everyone else to bugger off and have a completely closed system. They must look at the kindle with envy.
It'll be interesting to see how it plays out, whether we have a situation in a year or so where you you can only purchase and subscribe through itunes on iOS devices, while android devices offer choice and competition.
Just not having a proper kindle app would be enough to put me off getting an ipad.