What's interesting is Amit's post is the insight into how Google's team approached solving the problem.
1) Only blocking the site would not solve the underlying problem.
2) Sentiment analysis wouldn't solve the problem because reputation was coming from neutral news sites with solid reputations. Google has not yet found a useful way to incorporate sentiment into ranking.
3) Expose the reviews and ratings next to the results, but this would not actually alter the ranking.
Their new secret undisclosed fixed detected the problematic merchant and several hundred other bad apples.