One thing I thought of after posting was our reaction when someone does something that is "against the rules".
Getting other people to participate is truly the biggest challenge any wiki creator faces, the problems listed in my prior post are secondary.
I have been promoting wikis for over 10 years and have NEVER had anyone do something intentionally malicious.
They've made mistakes, but that is what they were, mistakes, honest mistakes.
Do you want to discourage them? Make them angry? There is a REALLY easy way to accomplish this:
Delete their post.
However, if you want to encourage them to continue to contribute, just change their behavior, there is a much more productive way to do it.
Communicate privately with them and let them know what needs to be changed.
Ask them to make the necessary changes, explaining the reasons why.
Be kind about it.
Thank them for participating.
Usually a lot of thought and effort goes into creating a wikipage,
Much more than most messages.
Respect their effort.