aristotle - 8:32 pm on Oct 10, 2012 (gmt 0)

Sand
I'm not sure that's completely true in all cases. Because panda is a specialized part of the algorithm aimed at content farms and similar sites. So it has a limited scope, Whereas Penguin apparently can hit any type of site. So Panda could catch a content farm-like site that passed Penguin, but not other types of sites that passed Penguin.