You can continuously vote as many times as you want. Each vote requires you to type in a six character validation code. Just for the heck of it, I voted for Steamtown three times in a row, pushing it to an even 2100 votes.

When you enter the site, the parks with the top votes are displayed along with the opportunity to vote for them. This probably leads to more votes for the leaders than if you had to look them up.

That 6 letter code? Commonly used to prevent automated signups? In the internet underworld, there are people who will solve those by the thousand for 60 cents per thousand. All it would take is one hacker who knew how to do that, and a few hundred bucks, to put his park on the leaderboard.