“The CTR on text ads declined about 60% in the last 2 months with Googles changes, Image ads on the other hand stayed the same.” –January 4th, 2008 Marcus of Plentyoffish.com
4 months later, that little back and forth in the Google Rec Room shaved about $85 Billion (with a B) in market capitalization.
But it wasn’t as stupid an idea as it might seem. You see, Adsense works in a Quasi-market place environment. The market will bid up the cost per click once the adjustment for accidental clicks is readjusted. Right now, marketers should be getting a better value per click as a higher percentage of the clicks are “real” or intentional. That will lead to higher bids per click and ultimately should be close to a break even for GOOGs bottom line.
SEO Black Hat (link)