Moving forward it's important to deoptimize everything.
We've been trained for so long to have perfectly optimized sites, because that's what used to work. The problem was the beast that Google had created as a result of having everyone trying to have "perfect optimization". This meant websites that weren't user friendly, content created for robots instead of users, and so on.
Penguin was created in order to reduce a sites rankings that is BLATANTLY trying to rank for certain keywords. Think of it like this, nobody likes the guy at the party that is loud, talking about himself, and generally being an attention whore. Before, Google was praising this guy and giving him the spotlight. Now, Google wants nothing to do with him.
Don't be that guy.