Control Panel "Password Security" option for Apple Powerbooks allows attackers with physical access to the machine to bypass the security by booting it with an emergency startup disk and using a disk editor to modify the on/off toggle or password in the aaaaaaaAPWD file, which is normally inaccessible.
http://www.securityfocus.com/bid/532
http://freaky.staticusers.net/macsec/data/powerbooksecurity-data.html