Pandora and Kindle both duplicate Apple services (iTunes & iBooks, respecitvely) to some degree. It's not particularly surprising that Apple wants to kick them out now. They've probably had this planned all along and ready to put into action once they got big enough.

What do you think your average iPhone or iPad owner is going to do in response to this change - buy a Kindle or Android device so they can keep using Pandora/Kindle, or just buy stuff from Apple's services instead?