No doubt about it, the new Groups feature holds a lot of potential for collaboration, including the ability to share documents. Here's an article that describes Groups, from PC World, a source I highly recommend:
New Facebook Groups: Key Facts about Facebook Groups | PC World
But today's news about Facebook founder Mark Zuckerberg being added to a group by someone else without his knowledge exposed a giant wart about the feature. Your friends can add you to a group without your knowledge. You can opt out, but you can't opt in.
PCWorld advises us about what to do:
Facebook's New Groups: 5 Things You Need to Know
The bottom line? “… using Facebook as a place to connect with people you actually know becomes more important than ever.”