While there are similarities between Instant Outlining (IO) and Wikis, there are subtle differences. Instant Outlining is more about people and relationships where Wikis are more about documents and collaboration. Instant Outlining is more about now and decentralization where Wikis are more about history and centralization.
I think the two can be combined to get the full benefits of both: a beast with multiple heads of Instant Outlines and the body of a Wiki with full versioning support. Ross, I think you need to ask Uncle Fluffy to tell you a story.