We had a client's website hit hard by the Penguin update, particularly on the 24th. Sitewide each keyword lost 10-20 positions. It was in #1 or #2 for the past couple years.
We optimize all of our websites onpage features well and within the whitehat realm. Since this was the only website affected out of 50+ other sites, I am guessing the penalty came directly from the backlink profile which was quite bad. The client had bought two other directory link package deals about 4 years ago which all of the incoming directory links have the exact same anchor text. I warned him this was completely unnatural and we only went after "natural-looking" links since then. Keep in mind these links were from 4+ years ago and did very little for rankings as we came into the picture.
Out of 143 root domain links, around 45 use the same anchor text in link.
We started with about 50 links total 2 years ago and have since built a very good quality profile, or so I thought. I was almost certain is was enough various anchor text to dilute it down.
I'm wondering if any of your websites that have been hit have a high amount of exact match anchor text. I can't believe Google would penalize just for linkbuilding because it seems to be an easy way to attack competitors but all my data is looking that way. Let me know your thoughts if any of your sites have been hit. Thanks