Media reports of vandalism on major public wiki sites are way out of proportion to the amount of overall activity on the sites. Yes, it does happen, but it is very rare. If you do have a vandalism problem, then you have a human relations, employee management issue rather than a technology one. If you make sure all wiki users have a login, then you can find the culprit quickly and take the appropriate action, which could range from simply suspending access for that account to disciplinary action for an errant employee. If someone does change a wiki page in a way that is deemed inappropriate, that page can be quickly and easily rolled back to the previous version.
Given the collaborative nature of a wiki, you may find heated discussions occurring in the wiki that would have previously been confined to private email or a face-to-face meeting. Your wiki administrators will have to set up ground rules and procedures to deal with things such as dueling edits or aggressive comment threads. However, experience has shown that most wiki communities are self-policing, and you should rarely need to put those policies into action.