>and if the user is not logged in then we can use the IP

How do you vote if you're not logged in?

>Better to use something else (But what?)

Anyone know how to get the mac-address with perl? Other than that, the ip is about the only way that I can come up with to confirm that the votes are not coming from the same place. Checking cookies would obviously not help, unless one is set for every vote cast, and then it's still not a secure system.