We record votes by IP address. One IP address is allowed one vote per entry, but a registered user can vote again.
Unfortunately, IP addresses are related to the actual internet connection and not a specific device within a home.
With two people in one home - only one of them can vote without registering. If they both register, they both can vote.
There is no information transmitted to us that can identify individual users, and we don't want to force everyone to register.
Other methods of tracking votes (cookies) are very easy to abuse, and it's important to us that voting is kept fair.
We will continue making instructions clearer to help people vote with as little trouble as possible.