I believe the answer is http://browsertoolkit.com/fault-tolerance.png http://browsertoolkit.com/fault-tolerance.png People are just trying to store data in the

I believe the answer is http://browsertoolkit.com/fault-tolerance.png http://browsertoolkit.com/fault-tolerance.png People are just trying to store data in the most efficient system possible. Using RDBMS software to store data only queried by primary key that you know will never need to be aggregated or dynamically queried can be overkill.