I like it. It removes the incentive to make multiple accounts to vote almost completely. Although, I assume that most people here vote in the best interest of NXT, so wouldn't a lot of people get their voting power reduced just because they always vote in the best interest of NXT (and thus are very likely to chose the same option)?

Maybe this is a fringe case and not common at all? This seems to work better in multi-option polls, where it is much less likely for two individuals to coincide often. Also, this scenario just came to mind: Suppose someone creates 1000 accounts for the purpose of voting. Can't he game this system by randomly voting on issues he doesn't care about (reducing similarity greatly and not really influencing the vote in anyway) and when one he cares about does come up, he points all 1000 accounts at the option he wants? Because of his previous random voting pattern, the system will not be able to detect that he is gaming this particular vote.

We would also have to maintain a separate ledger to hold the records of all the accounts that voted, correct? (Or use AM, but at 1000 bytes per message, the number of messages required would increase over time as more and more accounts vote) We could run a parallel blockchain (secured by the NXT network) that only records matters dealing with the voting system. Voting would cost min fee (1 NXT), and these payments will be paid out to forgers, encouraging them to take on the second blockchain.