After updating to Fedora 9 today, Autologin was disabled. It seems it has been deliberately taken out. The current fix for Gnome is as follows:

Edit /etc/gdm/custom.conf 

[daemon]
# http://live.gnome.org/GDM/2.22/Configuration
TimedLoginEnable=true
TimedLogin=yourusername
TimedLoginDelay=0

You might want to set the delay to a few seconds. More information here:
http://dnmouse.webs.com/autologin.html