"There are people who say that REA sold a large number of refrigerators--and later many other appliances."

This and the TVA are great examples of government providing or providing incentive for shared infrastructure. I am not really trying to argue either side here, but government does have a decent track record of providing services that, by their nature, are going to be shared and one could easily draw a distinction between that and investment in unproven technology.

Government's track record on unproven technology for a general market seems more mixed. I note "more general market" because there is a lot of aerospace technology developed for a specific defense applications that has been adopted more widely in the industry. As noted, though, it was developed for a specific reason rather than just to see if it could work. Others in private industry figured out a way to adapt those ideas to do something important to them. Where government seems to do okay at unfocused research is probably at the university level, with the extensive research funding in the sciences. That also seems to fall under the umbrella of developing interesting things but letting others apply and commercialize them.