NoSQL databases break all the old rules
Amazon SimpleDB, CouchDB, Google App Engine, and Persevere may have a better way of storing data for your Web appFollow @peterwayner
There are still some limitations to this project. While the front page of the project calls it "a distributed, fault-tolerant, and schema-free document-oriented database," you won't get the distribution and fault-tolerance without some manual intervention. The nice AJAX interface to CouchDB includes a form that you can fill out to replicate the database. It's not automatic yet.
This approach isn't as limiting as it might seem. As I was working with these databases, I soon began to see how anyone could layer on a security model at the client with the judicious use of some encryption. Empowering the client reduces the need for much security work at the server, something I wrote about in Translucent Databases.