In July, Google officially announced favicons within AdSense ads. So the ad units will show off the site’s favicon, if available, which should increase one’s click through rate.
But in September, when Google launched their new AdSense formats the favicons went missing.
Last night, Google quietly mentioned on Google+ that they are working on bringing back the favicons. They said the favicons will be added to the new ad formats in the future.
I wonder if the removal of the icons were on purpose, to stager the launch with a new ad format and then switch it up by adding these icons to increase CTR even more.
Forum discussion at Google+.