brinked - 8:50 pm on Oct 28, 2012 (gmt 0)
From my experience with a client is penguin punishes link schemes. My client used a SEO service and what they did was set up links on blogs in a link wheel fashion. Blogs were set up on networks that would link to his site and link to the next blog article that was just a spun version of the current article.
We removed tons of these and he has made significant imporvement (now on top of page 2 after being nowhere to be found).
Not a full recovery, but that is expected since we pretty much wiped out most of the links.
So from my very limited experience with penguin, I would say I see evidence of link schemes, spun articles, spammy blog networks all have a play in how penguin punished a site. Bottom line..stay away from cheap link building packages.