NoSQL is more than just the flavour of the month. There's no doubt that it's here to stay. But the movement is now experiencing growing pains.
In short, most variants of NoSQL have established a niche for themselves by creatively dropping one or more of the ACID constraints of traditional relational databases. Consequently, what they've gained on the swings in terms of features, they've lost on the roundabouts. Today, some of those shortcomings are becoming pain points, and the respective projects are attempting to layer the missing features on top of their existing products.
An expert view is that this is the wrong approach to take. Databases are complex beasts, and their features cannot be layered on, but engineered concurrently. It's a non-intuitive insight, but one that the greybeards of the industry have learnt through hard experience over decades.
It's very timely that one of the most respected names in the database field, IBM Fellow C Mohan, has stepped up to provide much-needed leadership and guidance to the NoSQL movement. His initial analysis and critique of NoSQL is on his blog (Part 1, Part 2, Part 3 and Part 4).
Mohan has promised to study individual NoSQL databases in more detail so as to understand their design nuances better. If he can then propose ways for these projects to enhance their capabilities in the most effective way, he would have succeeded in enabling a whole new wave of applications.
Here's wishing him all success!