Why not a Desktop on a GNU/Linux Server

[Anthony Simonelli <asimonelli7@yahoo.com>]

I am planning on running a Squid Proxy, Postfix,
Apache, webmail server here at my company and I was
wondering if it was alright to run a Desktop or just
X-Windows on this server.  I love using the
command-line and have become pretty proficient with it
(I always have a terminal open), but other people in
my department are not and a Desktop will help them out
a great deal.  They're used to a Windows NT type
interface.

I have always read that a desktop should not be
running on a server but there is never an explanation
as to why.  Is there any problem with running a
desktop on a server other than performance issues? 
The computer is a AMD 1.1 GHz with 1.256 GB RAM and
80GB drive with only 70 users so it should handle it
just fine.