There is a very long thread at Google AdSense Help discussions where publishers are accusing Google of taking a larger piece of the ad revenue share. Typically, when someone clicks on an AdSense ad, Google takes some of that revenue, while giving the remainder of the revenue to the publisher.
Some are suggesting that since a couple days ago, Google began taking as much as 90% of the revenue split. There are over 120 posts in the Google AdSense Help, with complaints.
Some suspect it might be a lingering issue from the high impression counts AdSense was reporting, but many don't think it is related.
There is no word from Google on the issue right now. We will continue to monitor things and keep you all posted.
Forum discussion at Google AdSense Help.