Who You Need to Start a Wiki

To start up a wiki, you need a few key people. You need someone to handle the hardware and software systems, such as a system administrator, developer, and/or power user. Then you need contributors to add content. After that, there are additional roles that can help ensure that your wiki is a success.

If your wiki will be large or complex, you may want to consult an information architect to lay out an initial outline and write up suggestions for how users can best contribute. 

You probably don't want to set up a wiki and just hope for the best. Cultivate a wiki champion or two to promote the wiki within the user community.

Keeping an eye on the wiki is important, so designate a wiki monitor to track all updates and changes and to generally make sure nothing is amiss. To keep the wiki neat and clean, use a wiki tender to go through and clean up typos and messy pages.

Terminology, Tools, and Roles Evolving at wikipatterns.com

wikipatterns.com  is a wiki that describes wikis and the evolving social ecosystem around them.  They list a variety of user roles.