grow your wiki
Also known as the Wiki Ninja, the Flying under the Radar pattern speaks to a successful adoption approach that many organizations have used when adopting wiki's. Specifically, hosting the wiki initially through unofficial channels, using a corporate credit card or other "black market" funding to pay for hosting, as well as using a set of community resources who are willing to play the role of Champion, Gardener, and other roles on their spare time.
The flying under the radar approach is particularly useful when introducing wiki's, blogs, or other Web 2.0 platforms to organizations that have very little history with using these tools. Getting a wiki up and running, releasing it to a small subset of users, and creating proven business value by actual usage can often be a quicker route to success than going through the multiple levels of bureaucracy necessary to installing, establishing and supporting the Web 2.0 solution. Because of their viral nature, this kind of approach can be incredibly successful within the enterprise.
Care should be taken, though, to recognize when this approach is no longer scaling to support the needs of the organization as a whole. At some point, Web 2.0 solutions, including wikis, need to be properly considered within the context of the entire enterprise, including existing platforms that might be providing similar function. Leadership will eventually need to be included. The emphasis should always be on on continual learning and change, and direction from all levels of the organization, preventing the solution from getting bogged down in an overly complex, top-down governance structure.
If you're finding it impossible to convince leadership within your organization that wikis are important and useful, or if your current organizational culture is very resistant to change, then do what you have to get your wiki up and running. Often it is much easier to prove value from a working system that has dedicated users. It's easier to ask for forgiveness for a successful unauthorized implementation than permission to get one started.