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Now if i was Adsense, and looking to have a sustainable business, there is no way i would continue with a site that was costing me more to service (spidering costs, server costs etc) than it was returning me in revenue. And i guess at 0.0 or very low click through rates combined with low CPC and impressions, that would certainly raise a "flag"
A lot i think may depends on your content "category". If you are one of many sites all servicing the same advertisers and there is not enough ads to go around then it's not good. However if you are in a unqiue niched category where there is too many ads for ad space (or if it was a "growing category" where i would like to enourage advertising growth - like say some b-to-b areas etc) then i would be more patient.