birchy - 9:56 pm on Jul 5, 2013 (gmt 0)
Progress report, on the original topic. After thrashing around, I've basically restored my site to its original setup, but with more space around the three banner ads that are used to break up the long list of tabular data, and I did turn of "enhanced text ads". My CTR had fallen to 1/10th of it's previous rate, and after 4 days has risen a little to about 1/5th (but that's a snapshot, no idea what it will be over the next week). Fortunately, my CPC has remained high, thanks to the page content. The clawbacks have almost stopped. There doesn't *seem* to be a 1:1 correlation with the extra space around ads and the clawback behavior, but I can only see into the black box so far. I've been thrashing around making all sorts of changes and we are in the middle of holiday traffic. I will try to report my situation status when more water has flowed under this bridge.
btw, as I ponder this whole issue, I'm guessing that mobile browsing is having some impact. It's a lot more likely to accidentally hit an ad while using a phone or tablet, scrolling and resizing images inside a tiny window. Perhaps, our pages will have to increase the white space around ads to minimize that, but Google will have to take that into account and allow for more invalid clicks in their algorithms.