Penguin 4.0 Update: What We Know So Far
 

With Penguin 4.0, changes will be visible much faster, typically taking effect shortly after Google re-crawls and re-indexes a page. Please read more details here : http://www.brainpulse.com/search_eng...user-guide.php

Penguin is so dangerous is because you will never be informed if your website is penalized. You can only assume that you were penalized by indirect signs like a sharp drop in organic traffic or declined positions for some of your keywords including the branded ones.

Penguin is so dangerous is because you will never be informed if your website is penalized.