In recent years a considerable amount of research has been devoted to formal theories of precedential constraint. In this note I consider a recent paper which explores the use of factor hierarchies in this connection. In that work it was shown both that cases constrained with the use of a hierarchy may be unconstrained if the hierarchy is flattened, and that cases unconstrained with a hierarchy may be constrained when the hierarchy is flattened. I discuss the nature of factor hierarchies and attempt to explain these results.