This is actually quite dangerous.
You can use GData to load the document retrieve all contributors and authors.<p>You can also retrieve the viewers using a cronjob.<p>GData returns  a "Person" objects in 3.0 
<a href="http://code.google.com/apis/gdata/javadoc/com/google/gdata/data/Person.html" rel="nofollow">http://code.google.com/apis/gdata/javadoc/com/google/gdata/d...</a><p>and when you know that google docs generates a revision for just clicking around 
you can retrieve all revisions and email addresses using 
<a href="http://code.google.com/apis/gdata/javadoc/com/google/gdata/data/docs/RevisionEntry.html" rel="nofollow">http://code.google.com/apis/gdata/javadoc/com/google/gdata/d...</a><p>Anyway, it is a great idea... but really not a good idea to use a google doc :-)