Despite all the signals, chatter and reporting showing that Google's search results appear to be updating as if there was an algorithmic change at Google, Google has told me that there is nothing going on.
Google said that they are not working on anything and there is nothing going on around this. They wouldn't comment more than that.
How can there be this much discussion and noise around a non-Google update? It has happened before. Either this is surrounded around normal algorithmic shifts without a refresh or update, maybe around link penalties or maybe Google is hiding something from us? I am not sure. I am just telling you that Google has denied this.
So if your site took a dive in the past week or so and you have no manual action, then it isn't real - it is fake. No, I am kidding, it obviously is real but we cannot attribute it to a confirmed Google update. In fact, it is Google saying there was no update.
Forum discussion at WebmasterWorld.