A use case for multi-server wiki is as follows -
The user chooses a MasterWiki?, and via that MasterWiki? subscribes to other wikis. The MasterWiki? maintains lists of which other wikis have pages for which WikiNames, so that it can efficiently display pages from all wikis that have pages for a given WikiName. All wiki links are given using the WikiUrlScheme. There is also a WikiServerUrlScheme and possible a WikiNoLocationUrlScheme -- PhilipDorrell.
See DistributedWiki