In the version of yum shipped with FC6 (3.0), the scripts to run yum via
nightly to pick up updates were removed in favor of the yum-updatesd
daemon, which runs all the time to watch for updates.  The new method is
more flexible and allows notification of the user via a dbus message to
a Windows Update style blinky button.

The cost of this new system is there's always a daemon running, the
defaults check every hour but don't actually download or install the
updates, and it gets in the way of manually running yum without starting
and stopping the service.  Handy for desktop users, especially those
used to windows.

However, the older cron-based, once-a-day system seems more appropriate
for servers or other remotely administered machines.  These simple files
from the old release restore this functionality.
