I saw Jacob Nielsen discussing the importance of breadcrumb trails and how they should be implemented.

We use the breadcrumb trail in our search and navigation solutions. It reflects the search that was done and any restrictions or facets that the user had selected. In the example below I searched for My Chemical Romance on Hot Topic, then selected Apparel then Band T-Shirts. You can see the bread crumb trail at the top reflects those selections.

hottopic BCT.JPG

We follow most of the guidelines that Jacob recommended. Because the facets don’t have any natural hierarchy we show them in the order in which they are selected. On the few times we have tried showing them in any other order we have always had complaints.