Sooner or later you are going to have to think how you structure your knowledge in your organisation.
This is for two reasons - for findability, and for ownership.
You structure your knowledge so that people can find what they need in a single place, and you structure your knowledge so that you can ensure that the key areas of knowledge are owned and maintained and connected to communities of practice. Yes, you can also have ontologies, taxonomies, folksonomy, etc etc - you can index and tag your knowledge in many ways - and structure is valuable also; if for no other reason than to give people access to the things they never thought to search for.
The choice of your overarching primary structure - the highest level of your taxonomy, and the way in which you divide ownership - depends on your organisation, and you have many options.
You can structure according to process, if you are a process-driven organisation or department. Knowledge is about process - how to do stuff - and is owned by process owners. Many of the oil companies, such as ConocoPhillips, use this structure.
You can structure according to equipment, if your role is to maintain and operate a piece of plant such as a nuclear power plant. Sellafield uses this structure for their configuration management knowledge.
You can structure around clients, or industry segments, if you are a sales organisation. Buckman labs use this structure for their Communities of Practice, as does Aon.
You can structure according to product or client offer, if you are a consulting or service organisation. we structure the knowledge in our Knoco knowledge base this way, as do the Big 5, as do oil sector service companies such as Schlumberger or Halliburton.
The key is to see which structure most fits your key knowledge, then ensure the knowledge base, the knowledge owners and the communities of practice are aligned with this.