As simple as furley's definition is, it is right on the money. Architecture, by its very nature, it totally concerned with the human relation to and response to a cumulation of "spaces" that allow activities to occur. Their job - beyond making it pretty, is to make sure people can function within the spaces and between the spaces.
While good architects focus on a balance between artistic expression and functionality, some architects get off balance and design nothing but foo-foo; artistic expression that is void of any useful or efficient space. These "bad" architects tend to make the building a "statement" instead of a habitat for humans. In other words, they let their ego get the best of them and ignore their clients true needs. While I haven't studied the layout and design fully, I would expect the triangular pyramid of glass at the Louvre in France a good example of a monument to someones self esteem.
Structural engineers, on the other hand, do exactly what furley states - don't let it fall down. Our systems and solutions do not always, or rarely, affect the client's activities and use of the building unless the project includes a lot of exposed structural elements. For most buildings, we structural folks are in the background, quietly supporting the architects dreams and (per ASCE's old motto) turning ideas into reality.