A wiki is a highly democratic medium. There is no easier way of killing it than imposing layers and layers of management upon it. Avoid managing your employees’ interest by making them “page patrons” or the like (so that each employee is responsible for some particular page or pages). If they are experts in some field, they will want to pass on their knowledge in one way or another. And if you can’t get some of them to put down what they know on a wiki page, well, maybe then a wiki is not the right way to do it (try making an interview-type podcast, most experts just love to talk about their work). Instead of putting up roles and rules, think of irritating a wiki by introducing a code of conduct (but be sure to put it in the wiki itself).
Steffen Blaschke: Wikis in Organisations