What are they? In a previous post I had suggested that the seeds to financial crises were sown by governments - the post singled out biotechnology and the War on Cancer. Lately, there have been signs that infrastructure such as gas lines, roads and bridges should be upgraded. In a previous post there were thoughts that the fiscal stimulus should have a larger infrastructure component. Meanwhile, Jeremy Stein points to renewable energy and its (futuristic) financing structure as a plausible scenario.
I would suggest only that some kind of government intervention in the form of subsidies or commissions are a necessary but not a sufficient condition. This is true in the current crisis as well in the form of the GSEs and despite strong protestations to the contrary. Something else is needed - just what it is would be good to know.
P.S. Some may claim that the Internet bubble occurred without any government intervention and I may have to concede on this point since I have not found any evidence of such. My response only would be that when the dot com boom was happening, the government fed the bubble by proclaiming that the high valuations were possible due to an increase in productivity (the so-called New Economy). Likewise, Bernanke's claims of a global savings glut was just a way of ignoring the problem.