I have Google authorship set up for a small hobby site (information). I noticed a drop from 2,000 impressions to 110 in one day. It dropped on the September 10th and is only getting lower. Anyone else noticed this? Is it an algo change? Also, I don't have very many Google Plus friends or whatever they are called.
Google referral traffic is down, but barely. So little that I don't think I can connect the two.
There is a chart that shows a correlation with Internet Explorer market share and the murder rate. This is why correlation is not causation. If you are looking for Google traffic I would focus on many other elements before spending time on Google authorship.