Is there a real answer to this question?
It does not matter what you or I feel. I would like to know if it is illegal as the question states.
I find it strange that ATT can have an exclusive deal with Apple to lock the phone. But if ATT does not live up to their contract and you leave, you are breaking the contract. In any contract deal when a party breaks it you can not transfer blame to the other side (meaning Me, the customer).
Also, I have bought the phone, in my case I did not have to pay the early termination fee (that part is to ATT's credit) most do have to pay an early termination fee. Once you have paid these you are no longer obligated to keep the phone locked to ATT. You have paid them for the phone and an agreement has been made between you and ATT for leaving.
Once that has been done you as a customer have every right to put that phone on another carrier.
Now, the reality. It does not matter our feelings. It does not matter the facts in my or your case. What matters is the law. What is it?
The first post explains that it is legal for us to jailbreak, unlock our phone. So, is ATT and Apple creating a product for our best interest? Are they going over and above their right or customary due in protecting their product?
It has been long noted that proprietary software is not the best way to go. It pisses customers off. The only advantage to it is when you have a captured market. It allows you to keep them longer and make more profits. It stops the do-it-yourselfers from doing it themselves and saving them money. It stops those that would build on their product to make a buck. Yet, smaller companies have a burst of popularity when they open their product, source code, etc and/or make it easy to use to the masses.
How did MS become so big. It was somewhere around word 2.0 they decided to open up other types of word processing and spreadsheet documents so you could modify that document. The catch was you could not save it back to the other kind of document. Most notably Word Perfect and lotus. That put word perfect and lotus out of business as a real competitor. Only when Microsoft began loosing customers again did they now allow you to save in other formats.
When a company cares more about jailing you into their product, are they truly out for your best interest as a customer? No!
One thing I will say about Apple. They have good products.