Check the wine site in my signature. There are two AdSense ads on each article page in the site. I don't usually put AdSense on home pages or category pages.
Here is something that is interesting. Yesterday I replaced the newer ad slot code with the old style AdSense code. I am now showing impressions and clicks for the wine site. I have not seen any impressions or clicks for that site since December.
It looks like there is something wrong with Google's recognition of their own ad slot code for some sites. I went through all of my sites that use AdSense. The only sites that are not registering impressions and clicks use the ad slot code, but I do have a couple of sites using the ad slot code that are registering impressions and clicks. Each of my sites is set up as a URL channel for tracking purposes. If you do not set up channels, you will never know if this is happening.
It does look like Google is not recognizing some sites using ad slot code.
I wonder how wide-spread this is. It appear to have been happening since December or January. If anyone has seen a decline in AdSense revenue since January, you need to check this out.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin