If the problem is hardware related, therefore NOT caused by a jailbreak, it should definitely still be covered by the warranty. If Apple doesn't like it, they should A) Make stronger devices B) Loosen the warranty to allow jailbreaking or C) Let cooler things into the App Store.
And SLC Flyfishing, you make it sound like Apple is some low company picking for change in the couch cushions so they can have enough money to make some new products. Apple has plenty of money. TONS of it, actually.
And jailbreaking is NOT illegal. Maybe to Apple it is, but they really can deal with it. How do you think a trial for someone who jailbroke their iPhone will hold up? It won't. It'll never happen.
If the problem with the iPhone was NOT your fault, then you deserve to have it replaced or repaired. That's kind of the point of a warranty.
Voiding your warranty because you jailbroke your iPhone is simply Apple's way of keeping a tight control on what you can and cannot do with your device. Nothing else.
Oh, and SLC Flyfishing: How exactly is Apple losing money if you want to have your device repaired because the home button broke or you have another hardware related problem? That hardware defect was going to appear whether your iPhone was jailbroken or not. So the people who have NOT jailbroken their device are NOT costing Apple money, but the people who did jailbreak it ARE costing Apple money, even though the jailbreak made absolutely no difference whatsoever?
Think some more. Please.