Implementing a voting system without requiring registration

Question

I\'d like to implement a voting system on my site, without having to force them to create an account. They would ultimately be voting up/down a piece of content which has a

Answer 1

It is impossible in principle for you, using a cookie, to distinguish between a visitor who has never visited and a visitor who has visited but deleted the cookie. Consequently, any cookie-based solution will be vulnerable to trivial vote fraud.

Consider embracing this reality in the spirit of J Henry Lowengard, who, when he setup the top 100 site on WFMU back in the mid-1990s, provided a button on the "your vote has been counted" page labeled "Go Back and Vote Some More!"

In fact, go there now and vote for (or against) StackOverflow!