Looking for help - scalability/reference usage?

Note - it was reccomended I post here by someone who is a big fan of pageblaster.  I think this is tough to answer since not a lot of people want to talk publicly about their sites, but I need some sort of reference account for an evaluation of DNN at work.

Here is the situation - I work for a non profit organization with many special interest groups that operate under the umbrella of the main entity.  We are in the midst of evaluating DNN versus Sharepoint for building our new community site.  The site is to have a main parent site, with approximately 100 subsites for each special interest group we are supporting.  Total number of users is around 400,000.

Here is the problem - DNN is doing quite well in the evaluation, but we have not been able to find any large scale sites for reference.  While the VP of IT is open to using open source in general, without a reference for a site of this size, he is falling into the "we know MS will work" camp.

Can anyone help?  We don't need names -  number of users, number of subsites and a rough idea of the system layout (number of front end servers, database specs, etc) would be really great.

Thanks in advance to anyone who can help out!

Thom Rossi
p.s.  I have been through the showcase sites on www.dotnetnuke.com and they tend to either be a single portal, or don't give any real detail as to their setup.

Hi Thom,

The biggest DNN site I know of is the official Australian Football site http://afl.com.au/

They have a webfarm with several front-end webservers.  They did need PageBlaster to handle their peak loads in season, but they have a ton of concurrent traffic.
I don't know specific numbers, but you can see from Alexa that they spike up very high.

One thing I would recommend if you are going to have a big site like this is that you have someone that knows about performance, load-balancing, and overall architecture of ASP.Net sites.