If the last few months of ranking changes have shown me anything, it’s that poorly executed link building strategy that many of us call white hat can be more dangerous than black-hat strategies like buying links. As a result of well intentioned but short-sighted link building, many sites have seen significant drops in rankings and traffic. Whether you employ link building tactics that are black, white, or any shade of grey, you can do yourself a favor by avoiding the appearance of link spam.
It’s become very obvious that recent updates hit sites that had overly aggressive link profiles. The types of sites that were almost exclusively within what I called the "danger zone" in a post about one month before Penguin hit. Highly unnatural anchor text and low-quality links are highly correlated, but anchor text appears to have been the focus.