Comcast FTL

Comcast's service has always been advertised as simply a maximum speed, with no stated limit on bandwidth. However if you're using too much bandwidth they will apparently send you a letter saying so. They don't tell you how much is too much, how to monitor it yourself, or even what things might be causing you to go over their mysterious limit, but if you haven't reduced your usage after a month they disconnect your service (and apparently won't give it back).

I think it's pretty shady to not mention in the Terms of Service that there's a bandwidth cap, and then enforce a bandwidth cap with no information about what it is.