Many Windows Phone app developers are reporting they have seen a massive drop in revenues from ads placed by Google's AdMob network in the past couple of weeks. At the moment, there's no word as to why this might be happening.
The reports are being posted on the Google Groups message board for Google Mobile Ads SDK Developers. One developer wrote that his ad fill rate from AdMob went down from 99% to just 7% in one day starting on May 5. So far, there's been no word from Google on what might be going on to cause these problems.
While some news reports on this situation have tried to suggest that this is some sort of deliberate action by Google, it's more than possible that a bug or other issue with the AdMob SDK is to blame. Hopefully, Google will make a statement on this situation soon.
Source: Google Groups; Thanks to everyone who tipped us!