Libertarianism and objectivism have always shared a somewhat uneasy relationship. Most libertarians, while acknowledging the importance and influence of Ayn Rand’s ideas, nonetheless feel a certain degree of discomfort with the more simplistic or dogmatic aspects of her message. In the words of Nick Gillespie, former editor of Reason Magazine, Rand is “one of the most important figures in the libertarian movement” and she “remains one of the best-selling and most widely influential figures in American thought and culture” in general and in libertarianism in particular. However he confessed that he is sometimes embarrassed by his magazine’s association with her ideas  .
On the other hand, Ayn Rand never cared to hide her disdain for libertarians, claiming that they used her ideas “with the teeth pulled out of them.” However, some of her ire may have been due to a misunderstanding of the term — according to Nathaniel Branden, Rand’s one time lover, she did not realize that libertarians were mostly advocates not of anarchism but of constitutionally limited government  . Many modern objectivists, meanwhile, continue to share Rand’s sentiments. In the words of popular blogger Gus Van Horn:
(The Libertarian) party is hardly a friend of liberty, given that their lack of a coherent philosophical approach makes them unable even to define the term… In essence, the Libertarians pretend that a concept as sophisticated and controversial as freedom is whatever anyone, no matter how mindless, wants it to be.
Elsewhere though, Van Horn describes himself as a (small-l) libertarian.
Van Horn’s dilemma is, I suspect, shared by most present-day objectivists. The heart of the matter is that libertarianism is a broad political ideology while objectivism is a closed philosophy. Objectivists value the basic tenet of individual freedom, but view it as a consequence of (in their view) more fundamental axioms. Thus, objectivism is a special kind of libertarianism, one that attempts to fit various libertarian principles as corollaries of a particular systematic philosophy.
In his very readable autobiographical essay, libertarian economist Bryan Caplan describes his shift away from objectivism.
I rejected Christianity because I determined that it was, to be blunt, idiotic. I rejected Objectivism and Austrianism, in contrast, as mixtures of deep truths and unfortunate mistakes.
During my undergraduate years, I spent far more time reading and thinking than writing. But two essays that appeared while I was in graduate school – “Why I Am Not an Objectivist” (by Michael Huemer), and “Why I Am Not an Austrian Economist” (by myself) – ultimately articulated the main objections I formed as an undergraduate.
Michael Huemer was a fellow Berkeley student, and the most powerful influence on my mature philosophical outlook; he is now a philosophy professor at the University of Colorado. You might say that Huemer provided a modern restatement of the Scottish philosophy of common sense, best represented by Thomas Reid, but this seriously understates the originality of Huemer’s contribution. In any case, like Reid, Huemer maintains that philosophers’ great error is to set up inherently unfulfillable standards for knowledge, and then turn to skepticism once they realize that their beliefs fall short of these standards. As Reid puts it:
[W]hen we attempt to prove, by direct argument, what is really self-evident, the reasoning will always be inconclusive; for it will either take for granted the thing to be proved, or something not more evident; and so, instead of giving strength to the conclusion, will rather tempt those to doubt of it who never did so before. (1872, p.637)
I do not think that Rand would have objected to Reid’s basic point. She maintained that there were three self-validating axioms – “Existence exists,” “Consciousness is conscious,” “A is A.” But for Reid and Huemer, the set of knowledge-not-in-need-of-proof is more expansive. In particular, it includes some moral truths. It is obvious, for example, that murder is wrong. If someone denied that it was obvious, what argument could convince him?
Rand of course thought she had an argument for the wrongness of murder (see “The Objectivist Ethics” in Rand (1964)). The more I reflected, though, the more I realized that her “man qua man” standard was question-begging. If Rand did not approve of an action that seemed plainly conducive to one’s self-interest, she declared it contrary to the life of “man qua man.” The Reid-Huemer route was to openly recognize the wrongness of murder as an independent moral fact. In the admittedly rare circumstances where murder serves one’s self-interest, it remains wrong.
Thus, the very systematic philosophy (‘leading’ to freedom) that objectivists view as their strength, Caplan sees as unnecessary and dogmatic.
My position on the matter is similar to Caplan’s. If one has to deal with purely moral questions, individual freedom needs no justification more basic than itself. However, there is no uniform route, moral or otherwise, to a political ideology. Libertarianism distills the essence of Ayn Rand’s philosophy — yet, by not imposing any further axioms, it retains a breadth that objectivism lacks. Thus, libertarianism comes in many different flavors — rights libertarianism, green libertarianism, consequentalism, anarcho-capitalism — each with its own philosophical underpinnings but united by the common thread of liberty. Van Horn and others may regard this as a weakness; however, I see it as a strength.