I personally found Dave's Blog post (http://community.plus.net/blog/2008/02/08/iplayer-usage-effect-a-bandwidth-explosion/) absolutely fascinating. The stats are scary. And as the El Reg article quite rightly points out, we don't yet have mass market adoption of iPlayer. But I bet the number of users is skyrocketing over time as BBC push it hard on TV / Radio and Online.
As more and more people catch on the bandwidth implications for ISPs are phenomincal and it can only be sustainable on a PAYG pricing model.
EDIT : To add link.
