I don't believe that's true. You can distribute Android applications outside of the Android Market. That means the cellular service providers would have to use network-based control mechanisms, which are safe and easy to circumvent (as opposed to jailbreaking, which requires you to be on constant alert regarding OS updates and when you can safely install them).
Moreover, after the Comcast-net neutrality fiasco, the FCC may be willing to rule against the service providers for implementing such restrictions. Congress is already looking into antitrust violations by the service providers (& the FCC into the banning of Google Voice on the iPhone), so I don't think such a move would be tolerated.
At which point the things that would dissuade people from developing for the iPhone will be outlawed. Which was kinda my point: Apple and AT&T aren't the only companies pulling stupid crap, and unless/until the landscape changes in a big way you're not going to be able to avoid stupid crap by switching carriers/platforms.
You misunderstand. While the network restrictions may be made illegal (on net neutrality principles), I don't see how anyone can force Apple to open up their App Store. As long as installing applications from sources outside of the App Store is not officially sanctioned, the iPhone will be at a disadvantage.
We saw how people reacted to AT&T's (legitimate) temporary block of img.4chan.org. If cellular service providers began blocking sites, there would be an enormous uproar. OTOH, everybody has accepted Apple's restrictions on the App Store (though that may partially be because of the RDF; if Microsoft had done something similar, I imagine that there would've been a much more negative reaction).
That doesn't stop people from doing whatever they want with their consoles (or their computers for that matter).
Sure it's a minority, but I suspect some day it will be the majority, as people stop letting companies get away with this kind of crap.
All mobile-phone platforms are still ultimately mediated by the carriers. If there's something they don't like, they'll find a way to stop you doing it; maybe it'll be an agreement with a hardware or software vendor, maybe it'll be implemented in the network, maybe it'll just be in their customer terms and give them a justification to cut you off. But they'll find a way to apply restrictions that will make people angry, because they can and because people jumping ship from Apple isn't going to change that.
And the alleged alternative at this point is Google. Google, which has a track record of simply shutting down accounts at their other services with no warning, no explanation, no appeal process and no recourse (unless you're lucky enough to know someone on the inside). Which makes "I'm going to develop for Android" sound an awful lot like "I want more of the same". Sure, you don't have to go through Google, but see the paragraph above for why it won't matter.