At first glance, PCs might seem almost vacuous, contributing almost nothing to the study of the design problem. However, this is not really the case. A common source of error in design is that the designers will forget to consider the impact of one or more PCs in their work. It is human nature: a designer will tend to focus on issues that are of particular importance to him, and expect someone else to take care of other issues. Sometimes, some issues will "fall through the cracks" resulting in a poor design.