I will bet anyone that the reason TW and other cable companies are trying to impose these caps is that they see the internet as a threat to their tv business. Think about it, watching your favorite shows over the net is becoming more popular all the time through sites such as Hulu. Movies are now being streamed over the net in SD and HD. Gaming consoles offer content through various services. The future is heading towards that way and these cable companies know it. Plus, it is a threat to their on demand services. So in response, they are looking to make money somewhere else besides tv and they know that bandwidth usage will only go up.
Another thing, they say that most people don't use much bandwidth. A couple things wrong with that argument. One, if it is only a few then what seems to be the problem in the first place. Two, even on the 1GB plan, the occassional user could blow that in a month just downloading updates. Think about it. Every bit of software nowadays uses the internet to update. Some of MS updates can be large as well as some game patches and updates. More things are connected to the net than ever before like your gaming console, TV, Bluray players just to name a few. So, it would appear to me, that TW realizes this and knows that people will "blow" the caps and either pay the hefty fee per GB or go up to a more expensive plan paying what they are paying now if not more and getting less service.