It is about time Apple put this out there. I've been worried about what I would do when enough of my computers die so that all of my authorizations were taken up. I really didn't want to have to create another iTunes account. Now, you can deauthorize all computers linked to your account once a year...
http://andylehman.blogspot.com/2007/12/itunes-authorizations.html
Thanks to xPunkx for this nugget.