It’s been confirmed that Google has blacklisted some ad buyers after exploiting their ad system, resulting in AdSense publishers noticing declines in their CPCs over the last few days.  The issue was addressed by Google y blacklisting those ad buyers and identifying the issue going forward.

Those affected by this saw their AdSense CPCs decline beginning on Sunday, August 5.  A Google posted a statement at WebmasterWorld:

Over the past 48 hours, a number of AdSense publishers alerted us to an issue with declining cost-per-click for ads on their sites. We were able to identify the issue and resolve it quickly: Several ad buyers were using irresponsible campaign parameters, lowering query coverage for specific creative types in some countries. The ad buyers responsible have been blacklisted and impacted publishers should see that their coverage is back to normal in their AdSense account.

These ad buyers seemed to be able to manipulate Google’s ad auction platform, resulting in the decline for publishers.  It let to both a decline in ad coverage and a drop in fill-rate, which is the reason behind the CPCs dropping along with it.  It was confirmed by Google that there was no user interface bug or reporting glitch.  Although the CPCs that were fairly low for publishers over the last few days won’t be updated, you should see CPCs that don’t surprise you going forward.

In the statement by Google, they said that the advertisers were using “irresponsible campaign parameters.”

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