[cookiecaper]

It's solely about the effort; it's a lot easier to just say redis.set('some_random_name') = value than it is to figure out where something should go in the schema of a RDBMS. If the data needs to persist, it needs to be written to a database that provides good guarantees about data integrity. If someone wants to load the results of a query into Redis, more power to them, but I've come across a lot of people who just stuff things in memory-backed K-V stores with the apparent expectation that nothing could ever happen to that data. Developers have told me "Well, Redis writes to disk on shutdown, right?" and acted like that was good enough for permanent storage of mission-critical data.

I have no fundamental opposition to K-V stores or NoSQL databases, but I do think most developers favor them because it's easier to stuff them with data up front. There are big tradeoffs down the road, though, which companies don't seem to understand well, and which they aren't really equipped to handle.

[nstart]

I unfortunately am not equipped with the knowledge about how people use/abuse redis like storage mechanisms. But that bit about how NoSQL is used as a point of upfront convenience is bam spot on. The biggest reason people have given me when I ask them why they want mongo is "easier to add columns".