There are dozens of threads at both Google AdSense Help and WebmasterWorld forums with publishers complaining about their CTR (click through rate) declining significantly in the past week or so. Some are saying this is having a huge impact on their earnings.
Here is what one publisher had to say:
My blog traffic still increasing but adsense earnings dropped from three days. I have a message from adsense help as "Your earnings were 76% below our forecast".
Here is another:
At the risk of getting screamed at for asking this question (yet again). My ctr went down the last 3 days (Sunday,Monday, Today) a whopping 75%!
Now, we always see complaints about CTR in the forums, but the complaints and pretty large now.
Personally, my CTR is up. Not that I do much with AdSense, but here is my charge, with a red line showing the trend:
RazorMax from the AdSense forums posted his opinion on what is going on over here.