Our client was approached about 6 weeks ago by someone wanting to sell him a position one ranking WordPress website.
The keyword was ” Osgood Schlatters Disease”. 
We analysed this site to find that he had NO external links. Just a loads of duplicated WP links. A trick (used to be) to add links, and have them appear on every category then add a post and click several categories. Lets see an example.
1 post – 8 categories = 8 pages – the links on that sidebar are being replicated 8 times per post.
It was easy to do with little effort.
Unlike my clients Osgood Schlatter Disease website: lots of real genuine information, good quality links built up over the last 3 years. Supporting information about the treatment (The Strickland Protocol) on Wikipedia.
This guy wanted in excess of $10k.
Penguin updates kicked in, and low and behold the other website vanished. This example goes to show that in some respects Google Penguin updates were well calculated and expelled junk.