I've just come accross this description of what an information architect is and I think it is the best I've seen so far!
The information architect is responsible for developing or helping to develop the information architecture for an information structure, in this case, for the Web. They have to strike a balance between the demands of authority (i.e., the clients the pages are being developed for), the demands of users, and the limits of information technology. The skill they apply is the knowledge of how to structure information effectively to improve its usability.And:
The purpose of the information architect on the team is to make sure that the design and content do not override the organizational structure. Information architecture is about the entire site, not the individual pages within the site. To learn to be an information architect is to learn to think in terms of the whole, rather than the elements.It turns out that it is part of a series of pages describing the craft of website design, by Peter Kantor whom I'd like to introduce as a member of the illustrious Peters in IA...