In wp-settings.php you can see this
(from line 268 to 278)
if ( '1' == $current_blog->deleted )
graceful_fail(__('This user has ...'));
For archived, deleted or spam blogs.
Maybe this can done with some graceful_redirection() function instead of graceful_fail()
The graceful_fail()just puts a text in a die()
(wp-includes/wp-mufunctions.php linea 1605)
In some cases, maybe I want to create a redirection instead of a page that simple say
"Moving along, nothing to see here"
And, thinking in the WPMU "motto", maybe someone move out from your free WPMU site, to a new blog (or domain) and like to keep a redirection in his old blog