I still don't understand the value add of MapReduce (in it's various implementations, including Hadoop) versus Clustered SQL. I see articles like this one that seem to imply that there is a niche for MapReduce for tasks like simple string search on super large data sets: http://gigaom.com/2009/04/14/mapreduce-vs-sql-its-not-one-or.... It just seems odd that people are so quick to throw away 40+ years of research on how to structure relational data and how to optimize queries against large data sets.