Reports are that LinkedIn will provide an API, opening up to developers a la Facebook. It may take nine months to do it. In my opinion, that may be too long to wait. Facebook has momentum now, and with their API, are capable of exerting extreme competitive pressure on LinkedIn now. Example: some months ago, LinkedIn implemented a feature called Answers that allows you to ask your network a question and receive answers from the people you trust. Within a week of the Facebook Platform launch, independent developer Jeremiah Robinson had created My Questions, a Facebook app that does substantially the same thing, by placing a question in your profile. LinkedIn is about jobs, resumes and connections. How long before we see Facebook Jobs, Facebook Resumes, and Facebook Introductions? And likely provided by third parties.
I wouldn't count LinkedIn out yet. They've got a pile of cash and a working business model. But like many others, much of my networking is moving to Facebook now. Nine months to an API is a long time.
UPDATE: Over lunch it was pointed out to me that Facebook Marketplace already implements jobs. Check!