[powera]

Facebook has never been good at explaining their products. Remember "Once every 100 years media changes"? That doesn't mean their products don't work. I've never had the impression that Facebook was overflowing with incredible technical challenges (well, they have scaling problems, but the impact there isn't user-visible), their brilliance has always been on the product side.

That said, first and foremost, Facebook is a contact management app. Allowing people externally to send messages to a FB account is the next step in managing contacts. The UI enhancements are unimportant in comparison.