With 500 million users worldwide, Facebook has proven itself to be a very innovative online tool that allows companies to interact with and even market to their existing and prospective customers.
Even non-profit organizations, publications (newspapers, magazines, blogs, etc), speakers, authors, musicians and more can use it to build and manage a following.
This is very easy to do because Facebook enables such entities to create "fan" pages (or what I call "brand" pages) - a customized profile page that allows them to share content, dialogue, photos, and resources. They can even launch custom apps, contests, and sign up forms - all from their very own fan page.