The growth of its user base and its ever-expanding

page views means an almost infinite inventory to sell. But the expanding supply, together with an equivocal demand, means ever-lowering costs. The math is sickeningly inevitable. Absent an earth-shaking idea, Facebook will look forward to slowing or declining growth in a tapped-out market, and ever-falling ad rates, both on the Web and (especially) in mobile. Facebook isn't Google; it's Yahoo or AOL.

...

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.