Lack of planning usually results in unorganized material and plenty of headaches along the way. Information Architecture is the practice of designing the infrastructure of a Web site, specifically the navigation. The title 'Information Architect' has quickly come out of obscurity and become a necessity in the art of web development. While one can go to school to obtain this title, the job can be performed reasonably well by following a certain amount of logic. Professional designers will benefit from architecture by being able to produce accurate quotes and preventing project overrun.
Many designers find that projects last far longer than originally projected.
This is a nightmare the careful planner can easily avoid. I'm a firm believer that one should go through plenty scraps of paper, if not a whole notepad, before the first keystroke or mouse click. I've built plenty of Web site in my career and have learned each time that the more planning, the smoother the project can be. If possible, have them sign off on the structure as you go. Every Web site has a purpose, a motive, a driving factor that prompted the need to put it on the web.