Last November, Google told its AdSense publishers that it would be switching how it pays them for the Google Ads they embed on their websites. Now, it seems like many AdSense publishers are noticing that Google has completely switched over to this new payment model. Note that not all are switched from CPC to CPM bidding fully.
Personally, on my AdSense account, I am still seeing bidding using CPC, in addition to CPM:
But many are seeing CPM at 100% of their bidding earnings.
A WebmasterWorld thread has publishers talking about it since the start of this month:
In the morning, have 100% CPM bids. CTR down.
I think my account is transfered do 100% CPM bids. Not see any CPC bids now. All is CPM.
100% CPM for me too. Looks like todays the day.
Same here, 100% CPM Bids but a decent Impression RPM.