Will they kick you out if your CTR is too low, for example if it was almost always .0%?! I moved them to the bottom of the pages because this was doing very poorley on my sites. I just want the $100.00 so I can dump them with out having to wait four months to get paid.
According to the Adsense terms of service which is agreed to before you are regstered and can get your code, Adsense can just about do anything they want! Im not saying that's good or bad, but the agreement is in the "contract".
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.