I think the important thing there is that breakthrough is really a question of timing. It's about technologies that are five or 10 years away from the market, so the market isn't going to finance the development. The most important thing is to think about the government's role to be able to support a diverse portfolio.
I think you're exactly right. You don't want the government in the position of micromanaging and picking whether technology A or technology B is going to be the winner.
The reason it's hard for these things that are further from the market to be able to finance themselves in the private sector is that in a single investment each firm is all in, right? If the investment fails, the company goes under. The government has the advantage of being able to support several technologies and to see which ones work—essentially, to let a thousand flowers bloom.
There was a nice study done by the National Academy of Sciences that looked at the research supported by the U.S. Department of Energy in the 1970s and 1980s. The great majority—I think probably over two-thirds—of the projects were unsuccessful, but if you look at the cost-benefit ratio for the program as a whole, it was a resounding success, because the few products that were successful were really big hits. That's really the idea: to be able to diversify to support a larger portfolio of projects than any one company could do on its own.