Luke Wroblewski at Functioning Form makes the case for value of design in communication, not just in styling. I like his word choice there. In his view, design abets the visual explanation of ideas, including the strategic direction of organizations.
It's a theme related to Idiagram's visual approach to knowledge, which I believe is much more fundamental than data visualization, and - to really stretch - the ongoing work by philosophers like David Chalmers, who might one day explain the phenomenal experience of beauty.
Design communicates. How it communicates is what interests me. I hope Luke Wroblewski will continue from his perspective to pursue answers to that question.