Sanity,
As my post says, I'm unaware of the legal precedent, so I can speak only as a technician: The analogy that I'm working with is that the recipient web server has the obligation of validating the TOS POST parameter and the entire POST form in order to accept (or reject) the users registration on behalf of the owners of their company. In a pre-web world, I wonder how much obligation is placed on say, a bank teller, who fails to notice a crossed-out term in a bank account obligation, and how that would translate to an online world.
Best,
Kevin