Mindfire
Istar
@Mindfire: You are right, and I think that I have figured out how it is exactly that the Slytherins cheat... That way it's possible to earn hundreds of House points in one hour, and I feel very tempted to do it for my House, but... No way, Ravenclaws don't cheat!
Apparently there used to be a huge thing about Slytherins infiltrating other houses under false aliases and then losing points on purpose so their own house would be ranked higher.