I can add a bit of background on this site also. 
As Cathal mentioned, they are running a huge webfarm, that is geographically dispersed because the anticipated traffic is very, very high during the sesaon peak as you can see from their Alexa graph  http://www.alexa.com/data/details/traffic_details?url=www.afl.com.au

A lot of the work done to make this site perform well enough using DotNetNuke has actually made it back into the core framework, and along with the recent performance changes in DotNetNuke they were able to get their load testing of the webfarm to deliver an impressive 36 Requests Per Second (RPS).

As I understand it, this was loading their DB cluster at about 80-90% of CPU.  At that point they were still kind of worried about making it through the peak of the season and I was contacted by Phil to see if PageBlaster could help.

As it turned out, after installing PageBlaster and setting the memory cache-interval for only 1 minute, the next load test ran at 366 RPS, and the DB cluster was running at around 20% CPU.

Anyway, sorry for beating my own drum, but I'm pretty excited about the results, and even more of a believer in the power of the ASP.Net framework's extensibility.