Well any iOS app you purchase can be installed on all of your iOS devices.
UNLESS, this is about how you can ONLY buy stuff from Apple's App Store and then I can understand the point being made. But jailbroken iPhone users are such a small percentage (as are rooted Android phone users) so I'm looking at this from the average consumers' perspective.
If they buy 100 apps on their Android device they are then leery about switching to iOS because they lose all those apps and vice-versa.
