freejung - 4:56 pm on Mar 6, 2011 (gmt 0)
Wow! Take a gander at some of those sites that people are reporting losses for. Go ahead and drill down to the MFA pages. I visited more than a few, all of them would have failed my initial sniff tests. Some of those folks have definitely stretched the limits of AdSense.
I agree that many of these sites have too much ad space, but there are several notable exceptions that lead me to suspect that ad space is not the primary factor here.
The one common thing I'm seeing in these sites has to do with overall look-and-feel and is hard to define, but it's basically this: upon landing on one of the internal pages of these sites, it's not immediately obvious that you've found the answer to your query (even in cases where a good answer really is there). This has to do with layout, typesetting and placement, which when badly done creat an overall impression of confusion.
My hypothesis, based on this, is that user interaction data of some kind is the primary factor here. People land on these pages and react negatively in some way that Google can measure as indicating "this page doesn't immediately appear to be what I want."