If it's too much complexity to track each user's preferences in terms of every other user's, you could also take a Bayesian filtering approach, similar to junk

If it's too much complexity to track each user's preferences in terms of every other user's, you could also take a Bayesian filtering approach, similar to junk mail controls, and compute a custom front page based on each individual user's prior upvotes/downvotes. In either case, the function of the voting mechanism will ultimately shift from generating the public front page to generating a custom view for each user. At that point, you could re-purpose the public front page as a selection mechanism to draw in the highest-quality users - perhaps by choosing a cohort of existing users to have public-upvote rights, or even by just applying old-fashioned editorial controls.