Quite honestly, the software lockout business model has been deserving of government scrutiny ever since Nintendo put a lockout chip in the NES. If you own a device you should be able to run any software you want on it.
Break it up, and then you may hear people complain about how the mobile app marketplace is too fragmented (similar to how video streaming currently is).
If I want iOS users to use my app, where can I publish it besides the App Store?
I like the Android implementation, allow users to install third-party apps but make them manually enable the feature, complete with warnings. Users don't have to enable the feature if they want App Store curation, but the option is there.
Yes Apple is, there is no alternative to the App Store on an iPhone.
Part of my confidence in the iOS app store is the fact that Apple controls it so strongly. If they were forced to allow third party apps I doubt I would install any. My phone is too critical a part of my life to risk it.