Not a lot of people seem aware of this. This is from the announce list. Please help spread the word.

The Fedora 12 release contained changes in the default PackageKit
behavior that allow installation of packages by users in cases where:

* the user is logged in on the local console, and
* is installing packages signed with a previously trusted key, and
* is using a previously configured and trusted repository

After more discussion and thought, though, the package maintainers
have posted to the fedora-devel-list mailing list agreeing to provide
an update to Fedora 12's PackageKit.  The update will require local
console users to enter the root password to install new software
packages.  Details on the changes are found here:

Paul W. Frields