When running an online voting site that doesn't really have any sort of user authentication method other than using cookies to see wheter the person has voted within the last hour. Data must be constantly scrutinized to ensure that no one is stuffing the ballot box.

To prevent bots from spaming votes, you need to use a CAPTCHA control like this one.

So, now people can't use bots to fill your ballot boxes anymore so are you safe from getting invalid votes?

No!

Do not underestimate the power of feminity! A properly equiped and highly trained female is about to convince legions of interested people to Click On Vote->Clear Cookies->Click On Vote... rinse and repeat.

Nothing against women but that's what the data is telling me. In fact the person doing it is getting so good at all that he's topping one entry every about 10 seconds, which after some tweaking of Firefox I too as able to do so it's humanly possible to stuff the box and there's nothing you can do about it without any sort of SERVER SIDE VALIDATION!