I strongly disagree with this view of document stores as 'easier' to work with.

For some tasks, this is undeniably true, but for most business problems I think this is just not the case. The profound irony behind this is that schema-less document stores wind-up being so much less flexible due to them being inherently very denormalized.

The good case for document stores is:

1. You have data that really is a blob independent of having relations 2. You need high-performance or map-reduce (Riak, Dynamo, etc.)

Those two use cases are really rare in the real world. For most people there's a huge amount of code that leans on RDBMS strengths such as:

1. Integrity constraints 2. Very flexible ad-hoc queries. 3. Decades worth of work on tooling to mitigate rough edges, and solve tough problems that have come up before.