Google adds "Discussions" into its cloud-based word processing service, Docs-- a shared commenting system some describe as a less complicated Google Wave.
The comment/chat feature allows multiple users to edit a single document (even simultaneously). Users can also invite new collaborators by simply putting their email address in a message-- while the system sends email notifications when one receives a reply to a thread or comment. Separate chat can also go on while users edit the document in question.
Google says the system should speed up document group editing-- and should roll out to all Gmail and Google App users within the next few days.
It reminds us a bit of what Google Wave was supposed to be-- the real-time chat and group editing system launched in beta in 2009. It was however found too complicated, and Google retired it (putting most of its code as open source) in August 2010.