Invariably, if there is a way to screw up your phone, my users will do, because they'll stumble on a website giving instructions on how to put this "marvelous" app on their phone.
Ah, so you're responsible for some people who you presumably have no real authority over, but you're allowed to choose their technology for them.
Why not allow your users to do what they want after promising (in writing) not to bother you about it? Some users get hand-held, some get to do what they want. Or why not simply factory-reset their phones if they screw them up?
Or, if you must lock them down, is it really the case that Android provides no such security here? After all, these are presumably the same people who, if not you, then some IT department somewhere lets them use PCs. Surely, then, even if it's by locking it down yourself, an open platform is manageable.
Ways to jailbreak your phone are security issues, nothing less, nothing more. Can you blame Apple from closing security vulnerabilities?
Nope, but I can blame them for setting up a situation in which a security vulnerability is what's required to "jailbreak" (read: liberate) my own device.
Where I live, every single Android phone has to be rootkitted in order to reinstall another kernel.
And where is that, exactly?
Motorola, among others, has pledged to ship unlocked bootloaders on new phones. You plug the phone in, run one command from the dev kit on a PC -- which will even work from a Linux PC -- to install an entire new copy of the OS.
Also, since when were we talking about kernels? I was talking about additional software. On iPhone, you have to jailbreak just to download an app that isn't from Apple's own app store. Not all Android devices require even the procedure I described above -- some allow you to download apps from a web browser the way PCs (and Macs) have for, well, forever. So, on some brand-new Android phones, I can take the phone out of the box, navigate to a competitor's app store website, and I'm good -- at worst, I download their app store client.
And for god's sake, Apple doesn't force anyone to do anything!!!! Nobody prevents anyone from using Android...
That's a bit like an abusive husband telling his battered wife that she didn't have to marry him. Yes, it's true that Apple can't stop me from buying Android, and no one was suggesting that they can. However, if I were to buy Apple, then I'd have these restrictions.
Furthermore, the more people who buy Apple, the more of a market there is for iOS apps, and the less of a market there is for Android apps. This affects me as a developer -- I don't want to be forced to publish through Apple, to submit every patch to their capricious review process. And before you say "Nobody is forced to..." Sure, it's not the case yet, but the smaller the iOS market, the more opportunities there will be for me to find employment, or for me to sell a solo killer app, to non-iOS platforms.