I don't think it would matter how many Free downvotes I had. I just went past the 500SP and my downvote would knock off a whopping $0.100 of a spammers payout. A person with 50SP may get lucky and be able to knock off a whopping $0.001 of a spam payout. So more downvotes are not going to help anyone other that the people with a lot of SP because then they would be able to downvote your account into the ground and not cost them a single penny. So free downvote=really really bad idea.