Just curious how many and what kind of servers does it take to run AVSForum? Is AVSForum the largest VBulletin deployment?

Hello...

AVS Forum is currently run on...

4 web servers that just server the PHP requests (each is a Duo Core with 2 gig ram)
1 MySQL server that is a Dual, Dual Core processors and 8 gigs RAM.
1 Web Image Server for all the images/gallery/and archives
1 Web Ad Server for the ads
1 Barracuda Spam Firewall that handles all the mail.
1 Barracuda Load Balancer that handles the traffic to each of the 4 web servers.

We are not the largest Vb site, but we are one of the most active with over 6 million unique visitors a month.

Hope this helps.

The 'Ad server' also supplies the data (for lack of the proper term) for the formatting commands for the replies?

Ad server offers nothing to the site operation other than the ad. Nothing to do with the site for replies or anything.