Take it personally: Yes, colleagues will edit your work and you might not agree with every change, but that's the nature of collaboration. It doesn't mean that your co-workers dislike you or think you're stupid.
Ignore questions: Colleagues may disagree with your changes and ask why you made them. If so, be prepared to give concrete reasons for your edits.
Delete useful content: Many times a posting can be improved by amending or editing it, but deleting content upsets people, and they may feel they've wasted their time.
Be chatty: A wiki shouldn't be used as a chat room. Any discussions related to a wiki subject should take place on the discussion or talk page, not on the actual content page.
Keep it secret: If you find valuable content on your company's wiki, tell others about it. Wikis benefit from a wide range of contributors.