I tend to oppose many government infrastructure efforts because the government has no incentive to do a realistic cost/benefit analysis of new projects. It is always in the legislator's and lobbyist's interest to start a new project, whether it be massive high speed rail lines, expensive green power installations, or large subsidies for classes of fuel and transportation that are uneconomical in the free market (hydrogen cars, corn ethanol). The only people paying a cost for new projects don't have a direct voice in the planning meetings.

The interstate highway system of the United States has long been the shining example of a "good" infrastructure project. But it has certainly subsidized the development of sprawling suburbs and a car-centric culture. Nowadays many expensive government infrastructure proposals (such as passenger rail) are aimed at mitigating the externalities from the earlier infrastructure projects. I wish we took a little more care at spending money wisely.