For those who may not know it, the site www.nrl.com is dedicated to Australian Rugby League (a football code).  Most of the time the performance is fine BUT if you were to visit the site during peak periods (ie; when games are about to finish) you'll find that (at times) its not so hot.  This is the time that most users will hit the site because they want to know the results of the games.  I often get my browser hanging on me during these periods.   While its not always bad during peak times there are definately some problems there.

So, as far as the scalabiity of DNN goes its not good enough to use monthly page hits and concurrent sessions.  What you need to measure is how well it performs when the concurrent sessions are requesting pages concurrently...  My guess is that it wont handle 30,000 concurrent sessions all actively requesting pages without some serious hardware backing it up.

Just my 2c worth.

Cheers