I would identify three categories of iconic architects. First, the four genuine starchitects at the beginning of the 21st century: Gehry, Foster, Hadid, and Koolhaas. Second, a group of about 30 signature architects (some of whom are likely to become genuine starchitects one day). These two groups are considered to be artists, whose designs are treated as genuine works of art, and unique architectural icons when they are built. The third group is made up of those who built what I conceptualize as typical icons, buildings that reproduce some of the elements that are just about recognizable to the untrained eye as similar to unique icons.
The starchitects, and to some extent the most celebrated signature architects provide the ideas that designers of typical icons copy.
Here, the Bilbao effect is important. This is the idea that if you attract a large cultural institution (for example, a branch of the Guggenheim museum), you will make your city more attractive for investment, brands, and tourism. The Bilbao effect has shown to be a major influence in persuading urban growth coalitions that it is necessary to have an iconic spectacular building, usually designed by a famous architect, to anchor urban megaprojects in cities all over the world (just as malls have always sought big-name stores/brands). Smaller and/or less well-endowed cities make do with typical icons.
The pros of the idea of the "starchitect" are that by treating globally iconic architects in the same way as celebrities in other cultural spheres, architecture is more easily represented as part of the general culture and begins to lose its taint as an esoteric art with little public interest. The cons are that by rebranding architecture in this way it can lead to an undermining of its high art status.
A consequence of this, as I document in my book The Icon Project, is that labeling a building as "iconic" and an architect as a "starchitect" has been seen by some as a negative judgement, by others as a positive accolade. It is important to understand that my analysis of these terms is sociological, and not intended as a judgment of architectural quality. For example, as I show in the book, it is often the less famous buildings of starchitects that other architects, historians, and critics rate most highly (good examples are Foster’s Willis Faber Offices in Ipswich, the Gehry House in Santa Monica, the Koolhaas Kunsthal in Rotterdam, and Zaha Hadid’s design for the Peak Club in Hong Kong).
On the question of the role of starchitects in the building and branding of cities, as I said above, the Bilbao Effect has been very important; the stardust of celebrity architecture and even the most successful typical icons rubs off onto the cities that can afford them. A less noted aspect of this which I highlight is the emergence of what I term "celebrity infrastructure" which is copied all over the world.
For more on this, read Leslie Sklair’s interview on World-Architects at www.world-architects.com