Just like you have with an SCM system, it would be cool to have version control capabilities in Buzzword.  So you'd be able to visually compare two versions of a document and see what has changed from version to version.  Then if you wanted to you could rollback to a previous version of merge two versions.  This becomes necessary when you have multiple people editing the same document.  Sometimes the document changes, but I don't have a good grasp on exactly what has changed since the last time or who made the changes.  I would want to see who made what changes when and then take actions as necessary.