The mega-trends, as summed up at Economics 21, seem to favor dynamic mobility providers over one-trade car companies.
Part of the longer-term problem facing GM and the U.S. automobile industry more broadly is that while automobile sales in emerging economies are increasing robustly, they are decreasing in the mature economies of Europe, North America, and Japan. Aging populations, deleveraging households, higher gasoline prices, denser metropolitan areas, and the advent of sharing platforms like Zipcar have dampened demand, and many if not all of these trends are likely to accelerate.
(via Reihan Salam at National Review)