CouchDB에서 나온 Map/Reduce를 찾아보니 아래와 같은 말이 나오네요. 

Map-Reduce is a technique designed for dealing with Big Data and processing in parallel in distributed systems.

요즘 추세가 Big Data 처리인것 같은데..

아래의 내용을 봐도 잘 이해가 안되네요.

http://www.slideshare.net/okurow/couchdb-mapreduce-13321353 

http://www.slideshare.net/Couchbase/couchbase-103-views-and-mapreduce  

http://cskstory.tistory.com/entry/%EB%A7%B5%EB%A6%AC%EB%93%80%EC%8A%A4-MapReduce-%EC%9D%B4%ED%95%B4%ED%95%98%EA%B8%B0