This is not about people innocently using a lot of data on an unlimited plan. This is a plan that offers unlimited phone data (and, so far, they really do mean unlimited) and 7 GB of high-speed tethered data. (After that, it's automatically throttled.) People in question are very aware of that 7 GB cap because they are installing special apps to circumvent its enforcement. The apps make tethered data look like phone data. That's not innocent and not OK.