I think MartinCron's point was that everyone always predicts Facebook's demise "three months into the future," and that this will also turn out to be nothing.
If that's the point, I disagree with him. We've seen far too many unstoppable behemoths collapse under their own weight to believe that anything is too big to fail. The difference between Facebook and, say, AOL, Yahoo, IBM, or any other company with a massive user base is that Facebook is run by a CEO with very little experience (compared to AOL, Yahoo, IBM, etc) and no fall-back plan that could let them remain profitable and relevant when their moment on top is over.