Does Apple have a monopoly that is preventing free and open trade? Perhaps. If so, government has a role to provide an open, honest shot for smartphone developers (and more so for end-consumers) This is because monopolies distort markets, which hurts everybody. But it's important to realize that for 99.9% of cases, having control over your platform, sales, and marketing channels is a good thing for everybody involved.
Should government enforce food labeling? Sure thing, because folks can't make an honest determination of what they're buying unless the contents are clearly labeled. This is back to the free and open market idea.
Should government step in anytime somebody (even a majority) think something is "unfair"? Not so much. People think all kinds of things are fair or unfair, and such distinctions are very emotional.
The key question is whether or not the iPhone is distorting the free and open market for smartphone apps. I think we have a long way to go before we cross that line. Right now it's more a matter of Apple doing wonderfuly well and holding their cards close as to what they want to allow on their platform. But there are a lot of choices out there for app developers and consumers. And the worse Apple acts, the more the market will punish it.
I'm a developer who's thinking about writing some smartphone apps. With all the publicity, I've decided that the iPhone platform isn't for me. Over time, if enough developers feel the same way, there'll be more apps not on the platform than on it. Apple has to be smart enough to see this as a problem, so I think things will be self-correcting.