This argument of David's

In short, the government takes whatever it can get away with, and it spends it on whatever it judges best.

together with this one

There are plenty of exciting things to do in space, and if anything, each of them draws more attention to the others

..have persuaded me to join in the 'hurrahs' for Mars.

So, hurrah!

Setting NASA the Mars goal will probably (and crucially) help to dissolve the regulatory opposition (that Gil rightly mentions) to private individuals wanting to do space stuff. I still think that, initially, private sponsorship will be reduced as the general public's gaze is fixed on NASA. But the eventual net effect of the first will be to encourage a space-faring culture. It will establish a moral imprimatur in the eyes of some politicians and offer a proof of principle to everybody else.

Perhaps Congress might consider funding some prizes to encourage the private individuals to join the race. How about $1 billion to the first private team to live on the moon for a month, and $3 billion for the team that makes it to Mars and back? These are tiny sums next to NASA's budget. We might even end up with a repeat of the Human Genome Project, where Craig Ventor pipped at the post the government-funded academic teams. (Congress should place the funds in independent trusts. This would avoid a repeat of some shameful history when the (English) Board of Longitude quibbled for a decade over rewarding John Harrison for his marine clock.)

Encouraging a space-faring culture might be an antidote to socialism, for two reasons. Firstly, if NASA suceeds, it will raise the psychological stakes for anti-Americanists around the world. Secondly, inhabiting distant reaches of the solar system is a great way to evade taxes. Perhaps it is a universal law that the only way to avert cultural stagnation is to start new colonies in distant places. We did this in New England and Hong Kong, and may perhaps do so in cyberspace. Such considerations should be set against the the morally-questionable funding of NASA.

Of course, as The World conceded straight away, the morally-questionable funding is going to be dreadfully inefficient. (By curious coincidence, the colonists of New England and Botany Bay were themselves morally-questionable in the eyes of those who stayed behind. Need only risk-takers and eccentrics apply?)

For the colonization of the cosmos to gather real momentum, apart from eccentric heroic participants, we'll need some superb innovations. History has shown that these always come from individual inventors and entrepreneurs. First off, we'll need launch systems that keep most of the power generation on the earth's surface. Then there's the hazard of sudden blasts of ionising radiation from sun activity. Then there's an awful lot of biotech to be done to (a) combat space fatigue, and (b) recycle food and atmosphere. The list goes on. We'll need to do a lot of GM (especially if we want to create some of Freeman Dyson's warm-blooded plants or similar such exotic delights). And we may even find that Mars isn't the best place to start and that the Kuiper Belt would be preferable...