It makes me want to...
It makes me want to start up my own ISP so I can inject some kiddie porn into the Rogers web site. I wonder how they'll feel about their wonderful new technology then!
I also wonder how long it will be before the ISPs start injecting code into each other's web pages? For example, an AT&T customer visits a Comcast page, clicks "Sign up" and gets redirected to an AT&T page explaining how great AT&T is and how much Comcast blows (or vice-versa).
In theory there is no difference between theory and practice, but in practice there is.