Okay, TR it looks like you're figures were pretty accurate. Here's my findings:

Minimum:

Contrib Modules: CCK: Content,CCK: Image,Devel,TAPIr,Google Analytics,Imagecache,Token,uBrowser,Workflow-NG
Drupal Core: Color,Help,Menu,Path,Taxonomy,Block,Filter,Node,System,User,Watchdog
Ubercart: Cart,Order,Product,Store,Product
Memory at devel_shutdown(): 12.04 MB

All Ubercart Modules (using beta 4):

Contrib Modules/Drupal Core: Same
Ubercart: All Modules
Memory at devel_shutdown(): 17.6 MB

All Ubercart Modules & Drupal Modules:

Contrib Modules: Same
Drupal Core/Ubercart: All Modules
Memory at devel_shutdown(): 20.88 MB

Not including other contrib modules people will want to use, I'd say those figures would be pretty good to use for the FAQ.