I discovered this quite by chance, but its actually a good case study on a law firm turning to wiki technology (in this case its Confluence again!) to solve identified business problems around knowledge sharing, collaboration and documentation - there is no social software hype here!
"As we started looking at new technologies, the flexibility and ease of use of wikis immediately caught our eye. A wiki would provide the kind of flexibility we needed for our documentation and allow us to create pages that were easily interlinked. Unfortunately, the pure wiki software we evaluated was, in many respects, too flexible. We found that one can end up with a huge, flat Web of pages linked to other pages without enough internal organization.
The anarchic nature of a wiki made it very difficult to build the structure we required. What we really needed was something in between a document management system, with its isolated and highly organized documents, and a wiki, with its ability to create and edit information easily in an ad hoc and unstructured manner."
When I read the case study I sense that this isn't so much about the success of social software, but more the about the success of the software product itself AND the evolution towards read/write intranets.