@Shepherd and @diberry: do you guys track the total amount of Google KWs you're receiving traffic on? Has there been an increase in the total amount of KWs (which may or may not translate into more overall traffic)
I am seeing some strange fluctuations in the amounts of KWs I get traffic from. Post-penguin the overall number of them has dropped significantly but some of them perform at the same level they've been for years. So, what happens is: when the total number of KWs drops, the good ones start bringing more traffic. When the total grows, the champions drop a little (not SERP, just the amount of clicks and therefore, I assume, impressions). So, the end result has been a pretty level amount of traffic. I also had post-penguin overnight 40% traffic drop in November. But if you consider the new overall level of traffic since November, it is also remarkably even.
It looks on a graph and feels pretty darn like traffic throttling to me.