If some advertisers shift from PPC to PPA, it sounds to me like there will be a drop in PPC prices. Which in turn may lead to revenue problems at many advertisi

If some advertisers shift from PPC to PPA, it sounds to me like there will be a drop in PPC prices. Which in turn may lead to revenue problems at many advertising supported sites. Also, not every site is suitable for PPA - since they won't convert well (domain parking being an extreme example). It will be interesting to see if there is any impact on Google's short term revenue.