Hypermiling for cable.
Remember the hypermiling craze? When gas went over four bucks lots of people got curious about extreme techniques for saving gas. What is to prevent the same mentality if and when caps become a problem? How many people will edit web pages drastically with ad and element blockers thereby saving the download bandwidth of ads, toolbars, annoying non-content clutter. And how will companies with a big interest in you seeing that clutter react? Sure, I realise that this is a tiny fraction of the bandwidth. But hyper-downloading will stress that "a bit here, a bit there" and eventually you have a saving. A the customer will at least have the feeling that he is doing something about his problem.
A suppose it will also be back to downloading divx and low res versions of non-critical newsgroup content and good-bye to 1080 mkv files. Maybe just as well. They never play the sound in sync anyway.