Jeffery Veen of Adaptive Path has written a great introduction, with examples, into the benefits of using fauceted classification .

“So often we assume that Web sites should be hierarchically organized. We talk about a “home page” that offers “top-level navigation” so that users can “drill down” to the content. It’s as if we’re programmed to think top down.

But what about information that isn’t as easily structured this way? Sometimes, content has many attributes that have different importance to different users. A hierarchy assumes everyone approaches these attributes the same way, but that’s often not the case.”

Read: Faucet Facets: A few best practices for designing multifaceted navigation systems