Alex Tabarrok observes:

In The Rational Optimist Matt Ridley asks:

Can you doubt that if NASA had not existed some rich man would by now have spent his fortune on a man-on-the-moon programme for the prestige alone?

In fact, we have some pretty good historical data on this issue. Bearing in mind that observatories are an early form of space exploration, Alex MacDonald, a NASA research economist, notes:

For the majority of its history, space exploration in America has been funded privately. The trend of wealthy individuals, such as Paul Allen, Jeff Bezos, Robert Bigelow, and Elon Musk, devoting some of their resources to the exploration of space is not an emerging one, it is the long-run, dominant trend which is now re-emerging.

MacDonald gives the following list of major observatories and their costs (click to enlarge).  Privately funded observatories are in bold.

Private spending on space exploration is even more impressive when we scale by personal wealth.

...rather than scaling the expenditure as a share of the total resources of the U.S. economy, the expenditure can be scaled as a share of the resources of the individuals who undertook the projects. James Lick was the richest man in California and the Lick Observatory expenditure represented 17.5% of his entire estate. The equivalent share of the wealth of the richest man in California today, Larry Ellison, is $3.9 billion dollars, approximately four times higher than the GDP equivalent share.

Private space exploration and commercialization are likely to increase substantially in this century and, perhaps surprisingly, President Obama is pushing NASA in this direction.  Here, for example, is a headline you don’t see very often, "Obama defends privatization of space travel."

What is really going on is contracting-out rather than privatization per se and as such there is significant room for abuse. Nevertheless, if done carefully, I think Obama’s efforts to encourage private efforts in space are a step in the right direction.  What would be much more welcome and useful, however, would be a titling system for establishing property rights in space (see also here).  Homesteading the highest frontier is our best bet for moving humanity off planet.

It would of course be a good thing if the colonisation of space happened due to the efforts of private agents instead of the state. In this context, we should not forget Herbert Spencer’s observation about traditional colonisation:

(H)istory presents us with proof that whilst government colonization is accompanied by endless miseries and abominations, colonization naturally carried on is free from these. Notwithstanding the misconduct he is accused of, to William Penn belongs the honour of having shown men that the kindness, justice, and truth of its inhabitants, are better safeguards to a colony than troops and fortifications and the bravery of governors. In all points Pennsylvania illustrates the equitable, as contrasted with the inequitable, mode of colonizing. It was founded not by the state, but by private individuals. It needed no mother-country protection, for it committed no breaches of the moral law. Its treaty with the Indians, described as “the only one ever concluded which was not ratified by an oath, and the only one that was never broken,” served it in better stead than any garrison. For the seventy years during which the Quakers retained the chief power, it enjoyed an immunity from that border warfare, with its concomitant losses, and fears, and bloodshed, to which other settlements were subject. On the other hand, its people maintained a friendly and mutually-beneficial intercourse with the natives; and, as a natural consequence of complete security, made unusually rapid progress in material prosperity.

That a like policy would have been similarly advantageous in other cases, may reasonably be inferred. No one can doubt, for instance, that had the East India Company been denied military aid and state-conferred privileges, both its own affairs, and the affairs of Hindostan, would have been in a far better condition than they now are. In sane longing for empire would never have burdened the Company with the enormous debt which at present paralyzes it. The energy that has been expended in aggressive wars would have been employed in developing the resources of the country. Unenervated by monopolies, trade would have been much more successful. The native rulers, influenced by a superior race on friendly terms with them, would have facilitated improvements; and we should not have seen, as now, rivers unnavigated, roads not bridged or metalled, and the proved capabilities of the soil neglected. Private enterprise would long ago have opened up these sources of wealth, as in fact it is at length doing, in spite of the discouragements thrown in its way by conquest-loving authorities. And had the settlers thus turned their attention wholly to the development of commerce, and conducted themselves peaceably, as their defenceless state would have compelled them to do, England would have been better supplied with raw materials, the markets for her goods would have enlarged, and something appreciable towards the civilization of the East would have been accomplished.

Of course Mars in the movie Total Recall is ruled by a private corporation with Coohagen as the corporate dictator, but it seems to be more like the rule of the East India Company than that of William Penn. And to be sure, it’s only a movie from a leftish director.

Not only is "natural" colonisation of space prefarable because it will probably free of the "miseries and abominations" of state-sponsored exploration, it will also be more optimal as a whole, as if led by an invisible hand. So when a commenter writes...

The Soviets would have arrived on the moon way before any privately funded person.

...one can only respond: so what? The Americans were in fact first to arrive. But that was the realisation of a political dream in the midst of the Cold War. It did not happen because it was economically efficient or because humanity really needed to put a man on the Moon. It happened only because JFK wanted it.  

Space exploration is fine with me, even for moving parts of humanity off this planet, if the need for it arrives. But please let private entreprise take care of it, instead of throwing tax payer money litteraly into space.

I can´t understand what hand is tellin about!