While I agree 40gb might be abuse of the network, at the same time Verizon (along with the smartphone makers/sellers/etc. in general) have said that people who root and abuse these things are a pretty extreme minority. Well we're talking about tethering here, but obviously to tether like this you need to root.
Anyways, there comes a time where it is abusive as opposed to feeling like we pay for what we're using. I think you may have crossed it, lol.
40GB is a lot though! And admittedly impressive, even if I don't support. I only use between 2-4 during the summer months, and MAYBE 6-7 during the school year for streaming music and killing time between/during boring classes. Actually, expect that 6-7 to rise this fall since I finally have Netflix.