The problem is that IA models information, not relationships. Many of the artifacts that IAs create: site maps, navigation systems, taxonomies, are information models built on the assumption that a single way to organize things can suit all users…one IA to rule them all, so to speak.
Thoughts on the Impending Death of Information Architecture
I could not agree more with the first sentence. Not enough thought is placed on the user's wants. We understand why this is so. We, the Information Architects, are surrounded by the business users, they are the ones that provide us with work; they are the ones that provide the goals and we, for better or worse, work off their understanding of what the customer needs.
Too often the business users have distinct wants that clash with IA goals. Ultimately the business users, who are writing the checks, make the final decision. An example would be users who want to go to your site for a quick piece of information and then leave. The business users on the other hand want to make their site "sticky"; or they want more page views so an unnecessary landing page is put in. These impediments help the business user meet his goals but often time hinders the user.
I have to disagree sharply with the following sentence that "information models [are] built on the assumption that a single way to organize things can suit all users." No Information Architect that I have ever met thinks this way.
The problem stems, not from IA in the abstract, but that IA is part-and-parcel of the business world. It's not that business is opposed to IA goals, only that IA is part of a whole and therefore, there are times, for good reasons or not, that other rationals trump usability.