People are already spending money working on private space flight on their own dime. I think if NASA spend a fraction of their normal budget on prizes, it will make technology develop much more quickly. I bet a private company could get a human colony on mars before the government (not saying the government shouldn't be involved when we get there). Competition breeds efficiency and innovation. Then again, private sector companies, while starting off by a bunch of ex-video-game-ceo-hippies would have a scientific intent, they'd eventually get overrun by greedy fucks who just want to make a profit.
Give private companies incentive to get us to goals, then let the gov't run that shit when we get there I guess.