If you think you need to pay people to work on your wiki, then you’re doing something wrong. Instead of trying to force your users to align with your business interests, by paying them, you should re-align your business interests to be more in tune with what potential contributors want and need. You shouldn’t have to pay for friends, and you shouldn’t have to pay for wiki contributors.
He also offers good alternatives to paying contributors.
UPDATE: it goes without saying, maybe, that this applies to any open project.