Depending on the application, using a document store with the ability to add indexes and/or perform ad-hoc queries can simplify things (something like MongoDB/CoucnDB rather than Cassandra). And sometimes just the convenience of being able to not need to define a schema using SQL or whatever ORM you are using makes using a NoSQL backend worth the pain of learning a new technology.<p>But there are a lot of existing tools for working with SQL technologies (PGAdmin on the Postgres side, MySQL Administrator in MySQL, etc.) that make the long-term use and administration of a SQL system much more manageable in the long term than some NoSQL options.