Facebook is a company of technologists, not marketers. If you wanted to bet on someone succeeding in the marketing business, you'd bet on technologists only if they could invent some new way to sell; you wouldn't bet on them to sell the way marketers have always sold.
As Facebook gluts an already glutted market, the fallacy of the Web as a profitable ad medium can no longer be overlooked. The crash will come. And Facebook—that putative transformer of worlds, which is, in reality, only an ad-driven site—will fall with everybody else.