Convergence - 5:05 pm on Jan 8, 2013 (gmt 0)
Started seeing a drop in traffic across websites we monitor and reports from other webmasters we know personally - this was on 3rd of January and 4th of January (US sites). Spidering from the Googlebot was minimal from end of December to the 3rd of January where it became heavy again (4-5 times the number of daily pages at the end of December).
Interestingly enough, no noticeable movement in the SERPs from 3rd January to 6th of January - but yesterday there was heavy activity.
Today is hard to judge regarding traffic as, so far, it appears to be a typical "Tuesday". But daily traffic is definitely down overall since the 3rd...