SMS is so ubiquitous because everyone with a (mobile) phone number can use it. IM always had this problem: some of your friends on MSN, some on AIM, etc.

I certainly agree there are opportunities for better FB integration into mobile devices but I don't think that translates to a viable business in making mobile phones (imho).

It's a bit like developing your own OS to compete with Windows because you want a better version of Outlook.