The same would have to be for downvotes as well (because they have to work in equal measure) which means this could also be an anti-bullying method! I hope @ned and @sneak will consider it. I completely agree that it could be a great solution to the current issues of imbalance between self interest and the interest of the wider community.
The only problem that I see with it is that it may encourage people to use sock puppet accounts. The average user probably wouldn't go to the effort of creating 100+ accounts but those who are currently invested with only their self interest in mind would definitely take advantage any way that they can.... The only thing I can think of that would discourage that would be the cost of creating the account, and so it really depends on how much SP is held by the sock puppeteer to make it worth their while. Take the badger accounts for example... There are 70 badger### accounts all belonging to one user with combined power of around 60 million SP... They could take turns forever upvoting each other. Sock puppet account would need to be disincentivised in order for it to work...