What if your pages have been pre categorised for certain search terms. For Christmas Gift your page might be assessed as a spam (OO) site but for keyboard gift it isn't. If I was a Google exec that would make me feel good "so you say that even spam sites are treated fairly! Great lets roll it our!" I can here him say.
We know that they have a list of Adsense/Adwords terms and in $ and basic reality terms they are probably the ones that are categorised and probably the ones that are subject to OO and spam.
Pre categorising pages off line makes a lot of sense as it makes earching really quick, reduces processing overhead etc.