If you look at Microsoft's anti-trust case (http://en.wikipedia.org/wiki/United_States_v._Microsoft) government imposed several rules on Microsoft e.g. required them to publish all protocols and APIs (e.g. Exchange protocol) so that other can create interoperable implementations. They were forbidden from doing different OEM pricing (so they couldn't strong arm OEMs by requesting that they pay more for a Windows license unless they make some concession in favor of Microsoft) etc.

More generally: "the Settlement's requirements were primarily designed to ensure there were stringent oversight procedures and explicit requirements to prevent Microsoft from engaging in "Predatory Behavior" or other practices that might form a "Barrier to Entry"".

It's not hard to identify Apple's 'predatory behavior' that creates 'barrier to entry' that could be rectified by government imposed rules.

One such 'predatory behavior' that creates 'barrier to entry' is inability to sell (or give away) applications that are not approved by Apple. Solution: Apple needs to allow installation of applications without approval by Apple. Technical solution: sideloading, third party stores like on Android.

Another 'predatory behavior' is the rule under discussion i.e. Apple disallowing all forms of commerce other than iTunes (which results in 30% tax to Apple). Solution: the rule needs to go away.

There are more predatory rules in the app store agreement (like inability to write interpreters which means no Firefox for iPhone) but they wouldn't be important as long as the biggest predatory rule was eliminated: inability to install apps that are not approved by Apple.