With an Apple account and an Internet connection, you can share your documents with people you choose. That's "share" not in the sense of emailing them or posting them on iWeb (both of which you can do), but "share" in the sense of posting them to the iWork.com public beta site where you can allow individuals to view them, comment on them, and even download them in formats like PDF and Microsoft Word. Now, working together on documents (Numbers, Pages, or Keynote documents) is easier than even before. The Internet takes care of the boundaries of time and space, while iWork with its ability to read and write documents in other formats lets people work with whatever tools they are comfortable with.
See the chapter on sharing in iWork '09 for Dummies for more details.