"We're seeing a lot of action in the key/value map/reduce world lately. On the one hand this is because simpler stuff scales more simply, and on the other because key/value and B-Tree stores map cleanly to some fundamental algorithms. At the heart of CouchDB's value proposition is incremental, peer-to-peer replication. All copies of a database are complete and can function independently at all times. Data can be shared with other nodes via replication, which can be triggered or run in continuous mode." - Peter Hoffmann from Bookmarklet