The short story is a person (not my client) was hit badly by Hummingbird. This was his message to google: How I know this is that he is a friend of a friend. Trust me you have never seen angry until you have seen him angry! He was absolutely LIVID when most of his keyword ranking disappeared overnight. Ironically his site has a nice backlink profile and very few spammy links, but he still got raped by Google.