1 - open a directory with ~7000 font (ttf) files
2 - open fonts:///
3 - switch to the directory with the 7000 files and hit ^a to select all 
4 - wait
5 - drag files to the fonts:/// directory
6 - observe nautilus taking 100% CPU with a 'preparing to copy' dialog box

The prepareing to copy may eventually go away, but I've waited for some time for
it and it hasn't, even on an athlon 2500+ machine with 1G of ram.   lsof shows a
lot open for nauiltus, but not beyond the normal libraries and so on.  IE: no
7000 files open or anything.  

The fact that I can do this copy in about 10 seconds by jumping into a terminal
do a cp Desktop/fonts ~/.fonts makes this a bit of a Bad Thing.  If it's
something with fontius and the rendering of every font file or something then
some of the performance issues should be looked at.  For example, opening the
directory with 7000 fonts takes far too long.  With one of the improvements in
nautilus being mime sniffing and better thumbnail creation, this should be
passed on to the other renderers within.

Fonts can be grabbed using http://forums.gentoo.org/viewtopic.php?t=161644 this
script for a 'real' test.