Mostly it's a knee-jerk reaction that all popoular things are usually just the tip of a huge iceberg of incremental improvements and other attempts at virtually the same stuff... But I did find something PARC-related:

http://dl.acm.org/citation.cfm?id=215706

Note the use of collaborative editing of text, and optimistic concurrency control for local changes.

> As far as I know, no one disputes the creation story of the first wiki as being by Ward Cunningham.

Nor that the first Model T Ford was created by Henry Ford :)

The only thing that comes to mind is Douglas Engelbart mother of all demo. It features a collaborative edition of a distributed document. Other than that, it seems Cunningham was the sole soul behind wikis.