If Apple chooses to take action on jailbreaking, then I will have to say that will be THE LAST day I own an iPhone. I like Apple products and I love the iPhone, but that is ridiculous. It's a hardware device, which means once I've paid you for said device... I can do with it as I please.
I could understand Apple saying that if you jailbreak it, we won't service your phone.. which I believe is the stance that they take at the moment.. but it is not, and should never be, illegal to modify a device that you've paid for.