A taxonomy is an organizing principle. It is a foundation on which to base any kind of system. It does not matter what kind of project you are involved in, it will benefit from clearly defined, concise language and terminology. A taxonomy and controlled vocabulary help to fine tune search tools, they creates a common language for sharing concepts, and it allows an efficient organization of documents and content across information sources.
Whether a structured tool such as a CRM system, or a less structured one, like a content management system that organizes information for web sites or intranets, all technologies that deal with information require a basis in taxonomy. This is even more important when various systems must interact.