graeme_p - 9:38 am on Jan 21, 2012 (gmt 0)
@potentialgeek, yes a 336x280.
It is the first large fall in traffic I have had in three years, and it came right on the day of the announcement, so I am inclined to attribute it to the change.
The announcement says that less than 1% of searches will be "noticeably" affected. A page of results that is only slightly different to a visitor, may be very significant to a site that has slipped a place or two down the page. 1% of searches could mean a lot more than 1 % of sites.
I would also be interested in knowing if this is completely rolled out or still going on, and whether there is any indication of what effect space taken up by things that are neither ads or main content has.