Good comment, but I wouldn't quite say that using a non-relational database frees you from having to think about a cohesive data model. It might be more accurate to say that for some data models non-relational stores are a more natural fit which frees you having to think about how to force your model into the wrong container.
It's hard to find the right adjective for what's distinct about the relational model.
The relational model is a fantastic model of data independent of application. It can even be a great model for an application using the same data in different ways.
But this approach clearly has a cost. In ways, there's the question - is this an application with a company built around it or a company with a application built around it? Digg and Google are applications with companies built around them. Here the RDMS model doesn't make sense.
