I absolutely agree with your point. If AT&T sees enough people leave them over this being the reason it will be changed quicker than you can type a reply to this conversation. However, both Verizon and AT&T clearly own the market share of subscribers and most likely won't be affected positively or negatively whether they choose to include or exclude this feature. This will be used as a marketing pitch for Sprint and T-Mobile as they are willing to do almost anything to woo new subscribers.

At no point is your hardware locked. If you're SIM is locked to a carrier your iPad remains functional whether you have an active subscription or not. The locking of a Sim card merely means that the data to a cell network is locked to that carrier. The hardware itself along with the use of Wi-Fi remains open and available.

Every carrier has it in their contract whether it's fair or not. As a subscriber to a carrier myself I am not agreeing that I like what they can do nor do I think it's fair. If you think that you really have rights with any carrier than you haven't read their contracts...

It is written on their website that you must have an existing tmobile plan of some sort to qualify for the 200mb of free data.

That's a nice sentiment. That will never be reality however. Whether it's convenient or not as long as you are not harassed while switching than a business has every right to try to sway you (within reason) and nothing you say or do will change that. The sprints and T-Mobiles of the world are only doing this because they are literally going bankrupt trying to get customers. If they were not so desperate they would not be so customer friendly.