I read the entry on the blog first, but it looks like this is getting some play and may get bigger http://www.threadwatch.org/node/4071
I found that very scary, particularly the comments by Rob Watts. I read, that if you opt out of image ads, you are also opting out of CPM. That's pretty scary. I suspect most Adsense users opting out of image ads, don't understand that implication and I've never seen it documented 'til there.
When I initially set up my account with adsense I choose both text and images however, I only ever use text ads... and I have never got any CPM ads on my site... so it seems even if you select image ads as an option you actually have to display them on your site to get CPM ads... is that what is being said... I would really love adsense to allow publisher more options... not just contextual ads... as I only ever get crappy Elvis wedding and Elvis Sunglasses ads... which pay 2 cents a piece... Would dearly love other ads to appear on my site.. however, even when I do create a page without the word Elvis appearing on the page I still get crappy Elvis ads... I am serious thinking of other ways of earning revenue from my site which get very decent traffic.... alas....
Honestly, I don't know. Not much at all has been said. Google should clear this up with a blog post on the Adsense blog.
I have seen on other channels where it says I earned revenue with no clicks, so I guess that's a yes.