They're not mutually exclusive. For example, I've done consulting work for a private geothermal energy LLC (AltaRock) that does a fair amount of R&D funded by t

They're not mutually exclusive. For example, I've done consulting work for a private geothermal energy LLC (AltaRock) that does a fair amount of R&D funded by the DOE (and maybe NSF?) and other public sources, though I believe that the company is also venture-backed. A lot of the hard part of the development in geothermal is fighting with problems that aren't very solved scientifically, particularly understanding the dynamics of stress and temperature in the upper several km of the earth's crust near active volcanoes. I was working with AltaRock on these issues, which are chewy enough that NSF doesn't consider the baseline levels of knowledge good enough to fund research in, as NSF wants science to be at a point where some sort of obvious scientific outcome is highly probable before they will fund it. I assume that this is pretty widespread in cutting-edge R&D: Those involved find themselves working at the ragged edge of the known universe, even if both academic scientists and the general public think of the topic as pretty mundane. So I view a fund like this one as quite complimentary to public funding: At some level, venture-type funding that has a high risk tolerance can help get projects off the ground to the point where they can get funding from both more conservative government funds and more typical institutional investors. (Full disclosure: I also own a private geoscience research company that solicits a lot of public funding as well as doing consulting and non-fundable research, but it's really just a shell for me to try to get paid to do cool science, rather than a nascent company focused on growth.)