[kellysutton]

We were also talking when writing the blog post that it depends on what the interface is for. When designing a site that accepts user-generated content (whether it be LayerVault or Facebook), the interface—is in many respects—only there to get out of the way. A flat design is often best at showcasing others' content.

When the interface is to facilitate a straight-forward task, one could make the argument for a more embellished interface.