I was also booted from Google for “inappropriate clicks” after an unusually high traffic day. I’m pretty sure my site was spidered (perhaps by Google – hah!) which caused my ad clicks to spike. When I pointed out that I had no way to control such a thing, the Google rep said they would not disclose their evidence, but that they have a proprietary system in place to detect abuse. When I suggested that they simply discount the clicks they think are fraudulent and let me stay in the system, the rep said they had a duty to protect their advertisers. I wish they cared as much about protecting their reputation and good will among the web folk who give them something to index.
The saddest part is knowing that I could boot anyone off their ad system by pointing a spider at their site. I thought Google was more clueful than that. Very disappointing.