One step too far
Up until now I've been on Apple's side in the debate. Unlike many Apple detractors on this site, I believe that having a partly walled garden isn't necessarily a bad thing for most consumers because of the vastly improved user experience it offers. Combine that with the fact that 99% of consumers don't care about being able to install hacked apps onto their hardware or do all those things that techies believe are essential.
iTunes app store has been a fantastic launching pad for many smaller software studios, allowing them to reach an audience they could never have dreamed of without Apples infrastructure. The 30% cut that apple take from these developers in return for distribution of their products is reasonable when you consider the cost to a small-time developer in infrastructure to do the same (and that isn't counting the potential marketing costs as well).
However, I believe that forcing content providers to manage their subscriptions via iTunes is one step too far. These are not apple's customers, they are the content providers customers, and the relationship belongs to the provider.
If Apple want a cut of this then the most they should expect is a fee from the provider per download of their app (in return for being an agent in the software distribution process). Whether the provider chooses to pass that fee on to the customer through charging for that app is up to them.
Apple are certainly playing a very dangerous game. As HTML 5 matures, providers will be able to migrate towards browser based products and continue to provide and similar level of end-user experience in their content. What will Apple do then? Block URL's in their web browser to those content providers services. The minute that happens they are dead in the water as a provider of the "mobile devices" that they claim is now their core business.
Come on Apple, you didn't create the content, don't expect a cut of the revenue.