How does ParticiPoll prevent audience members from voting more than once?

Participoll > Pre-Sales Questions
How does ParticiPoll prevent audience members from voting more than once?
The ParticiPoll voting pages use cookies to identify audience members and preventing them from voting more than once. If cookies are not enabled it will not record their vote. If a user tries to vote more than once it will just change their response to the most recently pressed option.