I went to a presentation about CouchDB recently, and afterward asked a couple questions about distribution, how views work, transactions, comparing its design and performance to RDBMSs, etc. It was immediately clear that the speaker didn't really understand the relational model at all (and he kept calling SQL "MySQL"). He couldn't answer several of my questions, but pointed out several times that the technology behind CouchDB is "way sexy". Now, I really like Postgres and SQLite, but I'm curious about the other systems because I'm a bit of a database nerd, and I was hoping he could explain what problems they solve, beyond some handwavey assertions about scaling and reassuring people with an aversion to SQL.
I'm not saying he's representative, but he comes to mind when I hear about a noSQL movement. People whose sole understanding of RDBMSs seems to have come from e.g. _PHP & MySQL For Dummies_, but keep hearing that SQL doesn't scale and noSQL databases are "the new hotness". Talk about the advantages of those systems compared to RDBMSs! And if you can't talk about any collective advantages they have, because they don't have much common ground (which is quite possible), then trying to present them collectively is just going to be confusing.
That may be a pretty big part of the explanation. Most of the apps build on knowlegde rathered in that book, would probably benefit from being released from the constraints of SQL (and on the level of a blog or forum app SQL is more of a constraint than a benefit).
So maybe NoSQL people need a movement after all. The relational people are at _least_ on their third manifesto. Lot of catching up to do!