Over the past 48 hours, there has been a spike in complaints around Google AdSense showing huge CPC, cost per click, declines after August 5th. There is a thread at WebmasterWorld and Google AdSense Help and a bunch of chatter on Twitter around this drop.

Many are saying they are seeing a 50 to 70% drop in their cost per clicks they are getting on the ads on their web sites. Google has not commented or replied to any of the complaints on social media yet.

Here are some of the comments:

Here are some tweets:

I checked my reports and it seems like the little I make on AdSense saw a drop as well in terms of CPC on August 6th and August 7th:

I am not sure if this is a reporting bug or something to come.

Google did publish a notice about annoying ads for AdSense publishers yesterday. I am not sure if that is related. I am working on an answer from Google.

Forum discussion at WebmasterWorld, Google AdSense Help and Twitter.

Update: @expressblogger share an email from Google they just received this morning:

Update 2: Google has confirmed the issue. Note, your CPCs will not change, it was not a reporting glitch. It does seem to be an issue with how some rouge advertisers were able to maybe game the system. So going forward, Google blacklisted these advertisers and hopefully closed this loophole they discovered. Here is Google’s statement:

Update 3: Want to know how this happened and who did it? I have more details in this new story.