> Allowing sideloading removes this protection, and apps installed that way could simply siphon all your data silently.

I don't have any iDevices, but are you suggesting that any iOS app has access to all of your files if the code makes it through the app store review? Because that would be a major issue in Apple's sandboxing in my opinion. I don't think you're right about how the OS security policies work, at least I hope so.