Guys! Look at that ugly penguin hiding...
Google is constantly changing (improving...) and this time many got a hit because of their new Penguin update. In my case, the latest changes have been rather positive, but many people got hit the wrong way around and their ranking went down, possibly very much so (some talk about receiving a negative ranking and suing Google over it!)
The latest change can affect anyone, although if you've done nothing wrong, you should be just fine. This being said, the way this new release works can lead to your website losing its rank because someone else played a trick on you. Whether Google can detect and/or accept that you weren't responsible is a different question. At this point, it is still a bit early to say that it is all bad.
So? What did they do this time?