Google has changed their algorithm once again. Recent algorithm changes include Panda and Penguin; however, the new algorithm, Hummingbird, is not just an update to their algorithm, but rather an entirely new algorithm altogether.
An article from search engine land goes into more detail about the algorithm and the severity of the change. Basically, Hummingbird allows Google to read search queries as a whole query in semantic search, rather than just patterns of letters. This allows Google to decipher intent of the query as opposed to what the exact key words are. The precise impact on SEO and keyword research has yet to be seen until there is more data post Hummingbird.