That was my point BigCrisco - they may not like the amount of data you are using with your illegal tether, but that's not the contractual reason they would terminate you. The contractual reason is that your ToS agreement that you signed says you can't tether another device without paying them to use it. So you would be terminated for breaking that agreement, plain and simple.
As I understand it they are now including new clauses to their ToS that let them throttle and/or terminate users that are in the top 5% of data usage for the network. I'm not sure how well either of those would hold up if they are trying to retroactively apply it, but for anyone signing a new contract it doesn't matter - if you sign a contract then you are contractually obligated, period (unless you can truly show they bargained illegally or made a truly unconscionable deal and hid it from you...but those are very hard to show and "not wanting to read the ToS" can't be construed as having it "hidden" from someone).
That's why I came up with my analogy - if you walk into a restaurant that has an all you can eat buffet and purchase the version that's all you can eat but doesn't include the premium food, you can't claim they are cheating you. When you order and pay for the lower cost all you can eat "plan" you can't go taking the fillet mignon unless you change your order with the waiter and pay the difference in cost.