According to xorg documentation http://www.x.org/releases/X11R7.6/doc/man/man5/xorg.conf.5.xhtml
/usr/share/X11/xorg.conf.d is for system use for vendors. The reason I put it in /usr/share/X11/xorg.conf.d is that I wanted to have the config files in one place. IMO it is not really a user config file it is needed to let the system run properly. Second /etc/X11/xorg.conf.d isn't created by default on ubuntu.
I can change it no problem, but I would rather leave it in  /usr/share/X11/xorg.conf.d