Something is amiss
I agree with those here who are making the point that Verizon is the carrier and they have the right to establish their plans and user agreements the way the see fit. And naturally, it does make sense for them to ask for more from users who will be tethering/hotspotting, as these users really are much more likely to be using quite a bit more data (and should therefore carry more of the financial load for keeping the network running). However, here is what doesn't make sense - the amount extra that they are charging.
Take a look at Clear Wire - They sell unlimited 4G mobile internet for $45/month ($55 for 3G/4G). So if I download 100GB of data off of their network within a month, my $45-$55 is able to cover that on their network (even if it requires averaging with all of the other users $/data usage). So then why is it that if I'm already paying in the neighbourhood of $80/month for Verizon's voice and unlimited data, I should have to pay $20 more for only 2GB? That seems retarded. And then $20 for each GB on top of that? By the time I've used 4GB, I may as well have just gotten Clear wire service on top of cell service, which seems stupid if I already carry around an Android phone. I can see paying a little bit more for the convenience of having the phone be my hotspot (and it is a lovely convenience), but for these usage fees, screw that. I'm either gonna tether out of contract or pay Clear Wire.
My hope is that Clear Wire is able to capitalize on this situation by digging into the wireless market. If they do, Verizon and others will be forced to stop being so asinine in their pricing.