Go ahead and start a site that hosts applications. You set the ground rule that if you want me to host your app you will pay be only 30% and you will get full distribution to millions of users. If you want you can even release the app for free and make money thru ads (that users will share with you)....some users however decide they want to use your distribution method but circumvent your charges by allowing you to go to a website and pay for additional services, or in the case of pandora pay entirely.....now, millions of people download pandora and say hundreds of thousands of people pay for the service. You only see money from ad revenue.....and not a penny from the paying users. Thats not cool since you are still hosting this app that is downloaded millions of times a day.
Get the idea if that happens over and over and over...eventually you are hosting a ton of "free" apps that people are paying for outside your jurisdiction. Not very fair and blatantly sidelining your terms of service agreement.
That is true and certainly a cause for concern for Apple (as a consumer it is great however). You did however neglect to mention that every single person that has downloaded that "free" application has already given hundreds of dollars to Apple to give them that privilege. Having applications like Pandora and Kindle and Netflix, etc. pushes forward the sales of the hardware devices because people can see that the content they want to be using is available for their device. Apple may not be getting the secondary benefit of those service's subscription revenue, but they have already seen a sizable benefit from having those apps available in the app store.
I have a feeling Apple has lets these things slide until now for just that reason. I doubt that someone at Apple just suddenly realized that these apps were in violation of the guidelines. There are a lot of people, including me, that would never have jumped on the iOS bandwagon if those apps were not available. Perhaps Apple feels they have a big enough customer base that those premium content providers are no longer needed.