Millsap thinks that:
When a developer is thinking about installing a database today because he need one to write his next feature, he wants something cheap, quick, and lightweight. None of those constraints really sounds like Oracle, does it?
I also think the main problem has been the idea of writing database independent code. That is, the developer wants to think of the database as a black-box. This is something Tom Kyte rails against in his books.
Millsap considers the biggest disadvantage of NoSQL databases to the lack of ACID properties, especially in the area of consistency.
However, I agree with Fabian Pascal, among others, that the biggest problem in the database world is the general ignorance about relational database theory. There are reasons that we do normalisation, have ACID, and complain that RDBMS are not relational.
I am following Millsap’s advice to learn about these NoSQL databases. To that end, I have read through Guide to Modern Databases and the NoSQL Movement. I probably should actually play with some of the databases described in the book.