whatson - 9:12 pm on Apr 18, 2011 (gmt 0)
One of my sites was hit quite badly, but a whole section of the site was not affected, believe it or not it was a gambling guide. The difference with the gambling guide is I have no ads on these pages (due to Adsense T&C), I also do not have any affiliate links on and monetize the gambling traffic in no way at all.
The rest of my site has reasonably heavy Adsense Ads. So this leads me to believe that ads play a major factor in this update.