This is a question that every usability specialist, information architect, user experience designer, human factors expert, etc. should be able to answer. What is the elevator pitch about what you do? How do we contribute to the bottom-line of a business? I used to ask this of every new hire. It is an important question, that demonstrates the person’s understanding of what the company does, what they do, and the perceived commercial value.
Adam Greenfield discusses in his recent posting. His brief overview of capitalism and the role of economic models and business requirements should be required reading for everyone working in user-centered design. It also makes it very clear that there is a reason that people "invest" in user-centered methodologies. And as professionals we need to be able to articulate our contribution to the bottom-line.