I'm starting to get tired of this mentality from service providers that, just because someone is using their services in ways they didn't expect, they're somehow 'abusing' the service. If you advertise the service as unlimited, it should be unlimited. You shouldn't care that I'm using it to torrent or do whatever.
If you can't provide a truly unlimited service, don't advertise it
Perhaps you don't think it is abusing the network, but I think it is. It's pretty difficult to use 2TB of data in a single month. These people are obviously using their cell phone data plans in lieu of a home network connection. They didn't pay for WiFi hotspot service. T-Mobile allows people to tether for free. A service for which I am greatly appreciative. But if you want to a cellular itnernet hotspot, buy one of T-Mobile's MiFi style plans. Don't turn your cellular phone + data plan into a MiFi plan because such abuse will cause T-Mobile to start charging people to tether.
People with your attitude caused Costco to update its return policy. It used to be that you could return any item to costco at any item, no questions asked. People abused this policy by buying giant HDTVs, keeping them for a year and then returning them to get a free upgrade. It was perfectly in line with Costco's policy, but it was obviously above and beyond the intent of the policy. Costco had to change its policy because it was being abused. If people keep this up, T-Mobile will have to change their tethering policy, too. If these people were not tethering then T-Mobile would not be complaining about their high data usage. I've certainly not had T-Mobile complain when I used my cell phone to download almost 100GB of audiobooks onto my phone in a single day. I bet they wouldn't have been happy if I tethered 100GB of data in a single day.