Well I think this depends on the pages...
For me the forums are just a secondary product.. I even modified the breadcrumbs so that "forum" only shows up IF you are actually browsing the forums
The MAIN thing for me are the profiles.. http://username.domain.com
IF a user goes to gallery its http://domain.com/gallery
Forums is http://domain.com/forums
The structure of the site is Home
------ User Control Panel
(havent finished the blog .htaccess to remove the "forum" in the url so the blog url will be http://domain.com/blogs/index.php
instead of http://domain.com/forums/blog.php
It took me quite some work to remove the word "forum" in the breadcrumbs from the Usercontrol Panel And from the vbulletin error messages!!!!!
The breadcrumbs on system and errormessages depend on THIS_SCRIPT where the error was generated...
Home --> Profiles --> Error or system message
Home --> Profiles --> UCP --> Error or system message
Home --> Forums --> Error or system message
Home --> Gallery --> Error or system message
Home --> Blog --> Error or system message
(still todo the contactus link.. that alway jumps back to forums-->contact us in the breadcrumbs
IT should be.. if invoked from gallery: Home--> Gallery --Contact us AND then redirect to the last page where you were that worked°°)
So if a user goes "Home" he should go to http://domain.com
because from there he can go anywhere.. So please DONT make it default..
IF a user wants to jump from gallery to forums.. he can use a navbar link!!!
But i agree it can depend on the type of site.. so if you do it.. make it an option...