If you see a score on a map and are certain it isn't possible, report it by posting to this topic. Include the map name or ID, the score poster name, and the score. Basically, make sure I can easily find the score in question. Note that sometimes impossible looking scores are in fact possible, so consider other scores on the same map for comparison.
Additionally, if you see a name on a high score chart that is not appropriate, report it here as well. I clean them up every now and then, but having specific examples always helps and spurs me into action.