Google Docs Email Collaborators

You have probably attached a Google Doc to a Gmail message via the weird little "Drive" icon button at the bottom left of the email interface:

Did you know you can also easily email any or all of the people who have access to a Google Doc, from within the Doc itself? Check out "Email collaborators" in the "File" menu:

This is one of those "anything you can do to make it easy for people to work together" features.