I don't really buy that. I have built applications using BDB on the back-end. It works really well for some things. It just has other shortcomings development-wise that usually makes up for the benefits and then some.

The thing is that object-oriented and relational design are fundamentally different. It is very rare to find people who are very good (or even equally good) at both. They are entirely different design disciplines aimed at very different problems. What non-relational db's do is they free the developer up from this second, very different discipine using tools that usually perform very well for standard OO operations.

That's a powerful thing.

Of course it's also powerful to have a math engine which can take your stored data, digest it, and spit out a report based on criteria you hadn't thought of until 30 seconds ago. And iterating through a collection of objects? Not a good way to do that.