I'm sure this will surprise no-one, but Google hasn't responded to my appeal as of today.
So I repeat: don't get into a position where you depend on Google for revenue. If you think ad revenue is a good business model, consider an ad partner who will avoid cutting you off for no apparent reason, and who will respond to questions if they do decide to take some unilateral actions. Google's too big and obviously overwhelmed with abuse -- but make no mistake; Google won't suffer if somebody does something fishy on your site. You will. (Or at least, I can only assume that's what happened to me -- since Google doesn't have the ability to tell me.)