Even in the event there is return on the investment, there's a risk that government becomes the rooster who thinks he made the sun come up because the sun came up when he crowed. The enterprise may have succeeded without any public investment. The fact the government was injecting dollars into the company or the idea in question might have just meant it was a hitchhiker along for the ride.
I guess I'm trying to ascertain whether there's any way to measure whether the presence of this money made a difference vis-à-vis the absence of this money. Maybe there's a control group that could isolate the effect of government action, but it seems hard even while looking at the rate of return to determine whether the government catalyzed the results in question.