First off, caps are not "virtually unheard of". Secondly Comcasts cap is 250GB/month. Who would use that in a few days? The biggest bandwidth eater I can think of is Netflix and a user would have to watch 108 movies in the best quality to reach that number.
I think your Netflix number must be wrong, because I work at an ISP and there are a lot of subscribers going over 250 GB/mo on Netflix. Anyway, one movie a day (or 3 TV episodes) on 4 computers is 120 movies/month.
