Downvoting
From NFSUnlimited.net Need for Speed Wiki
Downvoting is a practice used in the showroom or showroom challenges where a user rates all competing entries with the lowest possible score to get his entry ranked higher. Extreme cases of downvoting included multiple accounts combined with upvoting.
Downvoting was especially popular in Showroom v2 and was completely removed with Showroom v3 and first the reputation system and later star rating which both featured no negative votes.