grow your wiki
If this antipattern occurs, that might make an organization wiki-resistant for a long time afterwards.
Someone resource-rich enough or high enough in the organization gets displeased or impatient with the wiki developing "too slow" or in the "wrong" direction. So as a seemingly quick and painless solution one or more wiki users start getting paid specifically for creating, collecting or editing wiki content (or new people are recruited to handle these tasks). Right after the infusion of resources the wiki develops fine. In the long run, though, this means an almost certain death of that wiki as soon as the funding runs out - after all, why should anyone else work on the wiki, if it's those guys' paying job to do it, not ours...
Beforehand: You hear about this bright idea to start paying for wiki work.
After-the-fact: Only or almost only those who get paid to do wiki work are active on the wiki. There is a general disinterest towards the wiki outside their group.
If you hear about it beforehand and act fast, diplomatically and decisively enough, you may be able to prevent this from happening. Do your best to make the wiki attractive in itself: with interesting content, by minimizing demotivators, through some barnraising... And show this antipattern immediately, in private, preferably face-to-face, to everyone who suggests that people should be paid (extra) for wiki work. If necessary, speak against the idea also publicly, though preferably after you have talked with the suggester(s) privately.
If you don't recognize it before it happens, it may be too late to save that particular wiki.
This doesn't need to be a complete loss. You can "retire" it and start a new one, borrowing heavily from the content in the original. If you do this, be sure to either use a different wiki software, or heavily-reskin the new one so that it looks absolutely nothing like the old one. Hold public focus group meetings and ask people questions like "what could be done better". Make sure everyone knows that the new wiki is not the old wiki. Use the transition as an opportunity to encourage community involvement.
Let people know that you're fairly certain you know what went wrong with the last one. You can acknowledge, publicly enough, that paying for wiki work was a bad idea to begin with and that paying for wiki work runs counter to real collaboration. Then promise that the next wiki will be volunteer-only (wiki work included in normal salary) and keep that promise.
Would be needed here.