Nautilus not able to run as root?

["Michał Majchrowicz" <mmajchrowicz gmail com>]

Hi.
I noticed (on many different machines) that nautilus cannot be run by
root. Is it expected behaviour? When I am logged as user (i.e.) john
then when I do run in console nautilus window pops up (as expected).
But when I do something like this:
su
Enter root password
nautilus
Nothing happens :( The program just hangs...
Please tell me why it is like this?
Regards Michal.