Which games have been messed up in rankings so bad already then?
And well, I don't think it mathers that much to make protections against voting multiple times and making a system to make it able to change your vote and all...
Actually I don't think the whole voting thing mathers at all. The only time most people vote, is when the game is on the front page, when the game is on the front page, the game is just new and you haven't played it yet. So the ratings aren't possible to be reliable.
You may want to change your vote later, but as all other people probably won't, the influence of that vote is like from 0.1 to nothing at all. And the unreliability of the voting based on actually playing experience stays the same...
So well, imo it's no use in advancing the voting system as it doesn't get reliable by it and only costs more database space...