[garethmcc]

Non-relational databases match one of the largest use cases that exist; large volume OLTP workloads. Non-relational databases typically can handle far more load on reads and writes than relational databases due to their intrinsic distributed structure, meaning that if you have any kind of transactional workload, for example, a frontend to a busy store (such as Amazon.com), non-relational databases are incredible. You can also back these frontend non-relational stores with relational ones but at much smaller scale in order to handle the OLAP requirement where relational databases shine, allowing for massively flexible queries when needing to pull data for reporting etc.

[gregjor]

No disagreement from me. Relational doesn’t address every business requirement, nor do non-relational databases. They have enough overlap that you have to make an informed decision from experience.

The SQL vs. NoSQL debate got framed early on in terms of better and worse, old vs. new, which is unfortunate because it created ideological camps. Not every supposedly new thing is better than the old thing. Some NoSQL techniques predate relational databases, but no one younger than 50 has experience with what we did before Oracle and DB/2.

Choice of tools should match the requirements, not fads or anecdotes or personal preferences (or ignorance).