We have one client working with Ford that is using the wiki to draft requirements. They created a template, use it to start new requirements documents, and then work collaboratively with the clients to fill them out and update them. The permissions are tuned so only the appropriate team members have edit access to the specific wiki pages. The project is very efficient, and the customer is very happy to have full visibility into the process as it unfolds. They are now using wiki pages for other project deliverables like meeting notes, testing plans, and other important documents.