If they upvote a lot of spam sites, their account will have a low confidence rating, and won't influence each site's confidence. If they actually downvote a fe

If they upvote a lot of spam sites, their account will have a low confidence rating, and won't influence each site's confidence. If they actually downvote a few hundred spam sites before casting a vote for a spam site to promote it, then they will have built a 99.5% good database already and one site can be manually removed. The only way to have a high confidence in a user if they both downvote bad sites and upvote good sites. If they did that work to verify their accounts to be valid, then they will have done more good than harm