1script - 2:15 pm on Aug 8, 2012 (gmt 0)
By the way: the Search Queries report in WMT hasn't been updated in 6 days now - this is very peculiar. Calm before a storm?
Well, there has been some change here. In the last 12 hours the report had advanced 2 days for some sites and 1 day for others, which in itself is very interesting: I've never seen the results to become dis-synchronized across sites in the same WMT account.
Back to the main subject matter: I can only see one "zombie day" so far (Aug 2, 2012) but it shows that Google's own CTR is also lower. I know one day is not much statistically, but if the CTR holds, perhaps it is a hint that one of Google's latest algo changes has been detrimental for relevancy of Google's results. That would definitely result in decreased CTR across the board.
Actually, even the advertisers would be affected - bad traffic is bad for everyone. I noticed that on sites that run ads CPC and CPM went down sharply (~20%) on Aug 2nd. Apparently, bad traffic converts badly in every sense of the word "conversion" and it looks like those advertisers that watch trends very closely have noticed it right away. I would trust them - it's their money on the line...