An ambassador plays a critical role in wiki adoption by reaching out, in a positive and effective manner, to audiences and venues that have not yet fully embraced the wiki as collaborative authoring platform.
An ambassador may or may not be a Contributor to the wiki, but does endorse and grow the wiki through their actions. They are enthusiastic and appreciate the value of the wiki as a knowledge resource, and recommend its use to others. They never fail to reference the wiki as the source of their most prized information during presentations and communications.
When an Ambassador also is a contributor, it's possible they will become a coveted Champion in your organization.
A Spectator may develop into an Ambassador by being diligent about including links to wiki content that they've extracted. They may also encourage those who have something to add to the content to do so, themselves, at the original source on the wiki (and thus avoid generation of off-line supplemental documentation).