Facebook seems intent on "closing the barn door" and controlling the uber-social map. But can it be done? The real social map is so much bigger and more complex than what facebook knows. It includes my business relations social map (on LinkedIn), my acquaintances and info sources social map (on Twitter), and my Orioles fans social map (a bunch of curmudgeons and paranoid psychotics in the comments threads on the Baltimore Sun online). Facebook can't encompass that anymore than can master the complexity of the weather. Yes, their internal social map is explicit in their database, while the larger map is only implicit in my daily clicks and keystrokes--but that seeming advantage will prove trivial over time.
Another Facebook challenge: business and pleasure don't mix. People don't want pitches while their socializing. That's why LinkedIn is in such a great position. They provide much of the same functionality as facebook, but in an ecosystem where transaction is a benefit, not a nuisance.
And finally (not finally--there's so much more...) Facebook has a clarity problem. Their core value is their management of the social map. But they insist in controlling all the development that happens on top of that data, and even in trying to foist a new (and bad) operating system / interface on all who want to use that map. As a result, they fail to really harness the energy and inventiveness of the crowd. By trying to assert control over everything, they embrace an evolutionary dead-end. The fact that virtually all the apps built on the FB API are unrelentingly trite is not a coincidence, it's a symptom of a problem.