5
maybe a random key is a good idea if it can be implemented right..
or maybe a user could tie his computer name/id to the autologin cookie, that way a script could probably read the users computer name which could also be stored in the DB.. if the computer name of the user doesn't match the 1 stored in the DB then autologin will not function, but still would allow the user to login in a single session but not be autologged in, that way it would still allow users to login from another PC and if done on public computers there's no chance of them being auto logged in again.. of course the user should be able to change his computer id via a setting in control panel..