In January 2008, David DeWitt and Michael Stonebraker criticized MapReduce, claiming it to be a step backward in large-scale data applications. They argue that MapReduce lacks key features present in modern databases, such as schemas, high-level access languages, and indexing. By using brute force instead of indexing, MapReduce is seen as a poor implementation compared to existing grid-oriented SQL engines. Furthermore, the authors assert that MapReduce is not a novel concept, as its techniques are over 20 years old. They conclude by highlighting the incompatibility of MapReduce with standard DBMS tools, making it difficult to use in end-to-end tasks.
http://craig-henderson.blogspot.com/2009/11/dewitt-and-stonebrakers-mapreduce-major.html