OS X Account Settings Panther and Leopard (10.3/10.4)

OS X (10.3)

Accounts will not appear in the account list unless UID values are above 500.

OS X (10.4)

To hide an account:

sudo defaults write /Library/Preferences/com.apple.loginwindow HiddenUsersList -array-add account1

This will hide the user names, but has the side effect of adding a login called Other.

To prevent the Other login from appearing use:

sudo defaults write /Library/Preferences/com.apple.loginwindow SHOWOTHERUSERS_MANAGED -bool false

Unhide Accounts

To unhide all the names you may have previously hidden, you could execute the following from the command line.

sudo defaults delete /Library/Preferences/com.apple.loginwindow HiddenUsersList