First, let me preface this by saying that I am not one bit opposed to hacking the iPhone or any other consumer electronic device for that matter. However, I think people are making this whole issue WAY too complicated.
The reason Apple set up the iPhone to work with AT&T is because that is who they reached a mutual agreement with and it benefits them both. Same with any other cell phone that is designed for a specific carrier (Even if those are easier to unlock than the iPhone). The point is, though, that the agreement between these two companies was reached and since Apple created and owns the rights to creation of the iPhone, they can sell it however they like. That is the advantage of living in a free open market economy.
In order to ensure the software and hardware lives up to the standards that Apple has set (not the hacking community or the fan community) Apple (jsut like every other consumer electronic manufacturer) says in their liscense agreement basically "When you buy OUR product that WE made for a specific purpose, you are agreeing to use that product the way it was intended to be used. Any other use or alteration of that product is your choice, but we cannot be responsible for that."
Apple has a responsibility to update their product to their specifications and their's alone. All they have said is that our updates may render altered units inoperable. DUH! Without knowing what people have done, they can't guarantee the update will work. If you are using the item the way it was intended, they can guarantee it will work, because that is how they test. If you don't like the way the item works, then alter it and take the risk, or maybe, this is not the device for you and you should wait until the right device for you is out there. Those are your options, but the main point here is that it is YOUR choice.
American really needs to stop thinking aobut "Well, I'll sue" as the answer for everything and start thinking about who the responsibility really falls on.
Again, don't get me wrong, I am not against hacking at all. I have a hacked PSP, I have hacked electronics before, but every time I do, I realize that if I break it, I buy it. It's my fault for altering the purpose of the device, not the company's for not giving me free rights to do whatever I want to the product that they made, and then get mad when they don't support me for basically saying "Your product is not good enough, I need to change it, and I want you to fix it if I break it."
There I said my piece. Let the flaming begin, becasue I know it's coming. Just try to realize what I am saying, and not misunderstand what many may think I am saying.