I just happened to chance upon much hyped WriteBoard from 37Signals.

It is an online (ajax enabled; what isn't these days?) service to create and edit text documents with a wiki like syntax. It allows commenting on the document. Additionally it provides RSS feeds.

The key value proposition is collaborative editing of text documents and version control.

It looks to me like a wiki; pretty much everything it has can be done with a modern wiki software.

Here is my test writeboard.

Frankly I couldn't see what all the hype was about.