Architects versus developers (an architects perspective):

Ideas versus money. That is about the simplest way to distinguish the two and also the easiest way to understand why these two groups need each other. While overlap is of course possible, it is not likely. Developers frequently look at a potential project and create a general concept based on location and possible use of the land. Architects then provide a design concept to realize that opportunity and eventually the detailed plans to actually build the initial vision of the developer. Most projects, residential, commercial or otherwise, were created by the synergy of these two groups.

An Architect as developer has solved the financial puzzle and can move forward not just with the idea and concept, but the execution of the project as well; a developer as architect first must obtain required licenses and typically look beyond function of the project to integration of concept into a larger scope and environment.