Thus spake "Christensen, Courtney":
Would you be comfortable writing an extension to MediaWiki? I believe you co uld put the addresses in a custom tag that checked the user's rights before d isplaying the link. If anonymous users were able to view wiki-text they coul d still see the email addresses, but I think you can turn that off and it's a nother non-standard step to keep them away.
-Courtney
I'm willing to write an extension to do this if there isn't already a way.