Facebook is becoming the Borg -- you had better embrace the collective and make the best of it, or it will find your brand and build its community. Companies need to apply the same business sense, crisis management, and strategic planning they would to any brand messaging, marketing campaign, or customer-service protocol. Perhaps even more forethought is needed when it comes to social media, as customers will "talk back" and companies need to be prepared.
This is especially true when it comes to customers posting their ideas, suggestions, concerns or problems on your wall. If your business is primarily communicating with customers via wall posts and you have a large fan base, you run the risk of coming across as unresponsive, or worse, not listening if a response is not timely.
One other missed opportunity I've been noticing is the high number of businesses not using Facebook to leverage their corporate brand.
To illustrate this further, you can read about three companies that are failing when it comes to marketing on Facebook: Tesla Motors, Netflix, and Goldman Sachs.