re: When NoSQL Makes Sense
I just had a chat with Matt Pfeil, co-founder of DataStax, who took some exception to my classification of four NoSQL database types as detailed in the full (downloaded) article. He says Cassandra really started as a key value store and had functionality added to handle wide-column use cases. The same is true of most wide-column products, Pfeil said, and the key point is that Cassandra and wide-column databases can address key-value use cases. In his view, the boundary between key value and wide-column isn't really important.
I'd make the point that the key-value products that don't handle wide column (more complex data) use cases shouldn't be in the same category. Maybe "wide column" undersells the capability of such databases, but eliminating the distinction would seem to oversell the capabilities of simple key value stores.