If you RTFA, you'll see that the reason that they wanted to do the no password for signed packages was because if you always have to type in your password to install something, after awhile you just get in the habit of typing in your password whenever that little window pops up.
Actually the reason for this is that there is a more fundamental rewrite of the DeviceKit and PackageKit systems in Fedora underway which will eventually allow more flexible allocation of system admin privileges to different classes of user. This is a good thing.
However - when F12 was released this rewrite was only partially complete. The backend systems were pretty much all in place but the front end which allows the editing of rules and the assignment of roles had not been written. Fedora was therefore shipped with a default set of rules.
Under the new system the previous behaviour of asking for the root password, but allowing the option to not be asked for it again in future had been removed (for fear of creating a 'make it up as you go along' security policy). The decision therefore had to be made to either allow console (not remote) users to install signed packages with no authentication required, or to require the root password for every install. The developers chose the first option. This has now been changed to the second option.
I'm kind of ambivalent about the light this sheds on Fedora. It's a bad thing to have happened, but it was sorted out quickly and there is now much discussion about setting up a firmer security policy so this won't happen again. Mistakes happen, but as long as they are spotted and corrected then we should all just move along.