SSH forwarding of X question

[Bart Silverstrim]

Here's a silly question.

I thought that because of locality of reference, I thought that if I 
were on one computer and logged into another and launched an X 
application and went to print, it would use the other system's printer. 
  Instead, I'm getting my local one...why?

I am on one computer in my physically local network (for example, 
Superman).  I want to log into a system in another network named 
Spider-Man.  Both are running Ubuntu 7.04.

ssh -X -C myusername at spider-man-network.com

I log in, execute mozilla-firefox.  After a pause, firefox pops up.  go 
to a web page.  Go to file->print.  The printers available to 
Spider-Man, I get the printers installed on Superman here.

Any explanation?

-Bart