Thanks for the info falko!
Do the main servers monitor each other in the same manor as the load balancers for the high availability apache cluster how-to? Is rsync being used to keep both servers in sync? (most likely I guess) Are the databases set up in a master/master replication? This is all very interesting, really. An "How we do it here" how-to may be insightful for others especially if you could provide some general statistics on bandwidth being used, typical online user numbers and other such site related data. For my own purposes this data wont be as relevant but I have seen many discussions between people using forum software package such as Vbulletin or Drupal CMS packages that need to scale upward and are not sure what is needed.
Hopefully I'm not the only person here interested in this information. (would feel guilty asking so many questions otherwise) lol