Splugged - 12:08 am on Dec 12, 2012 (gmt 0)
Definitively something happened starting from Dec 8th.
My quick story:
-I had a decline in traffic on Dec 8th, about from 22:00 PM to 04:00 AM (Dec 9th) local time, Europe.
-I had some "hourly rushes" on whole Dec 9th (around 01:00 PM I had a classic pre-penguin traffic, 80-100 hits).
-I had another progressive decline from Dec 9th (around 07:00 PM) until today (-90% compared to yesterday). As for now, I had another "rush" about one hour ago (11:00 PM, Local Time, Europe).
Below there is the graph of impressions from GWT updated on Dec 9th.
Screenshot just taken: [i49.tinypic.com ]