David's post raises the perennial issue of what term libertarians should use to refer to themselves. I propose the radical option of embracing the term by which we are already known to 90% of the people who know about us at all: libertarian.
If I were writing on a blank slate, I would argue that we should opt for the terminology favored by F.A. Hayek and Milton Friedman and still used in Australia and many European countries: what we call libertarians should be called "liberals," today's liberals should be called "social democrats" (as they are in most of Europe), and the nonlibertarian right can continue to be known as "conservatives," while the word "conservative" should NOT be used to refer to libertarians. Hayek even wrote an essay entitled "Why I am Not a Conservative" to explain the differences between conservatism and liberalism/libertarianism; most of his points are highly relevant today.
However, Hayek and Friedman lost this terminological battle a long time ago, and I'm not sure we should want the term "liberal" back today even if we could have it. After all, the word now has such negative associations that even many liberals (in the modern sense of the word) no longer use it and have instead taken to calling themselves "progressives."
Sticking to "libertarian" avoids the substantial annoyance and cost of trying to change the language. Moreover, the term has important positive connotations because of the link to the word "liberty," traditionally perhaps the most important of American values and among the most important principles of Western civilization more generally. The other terms proposed by various people are either awkward ("market liberal"), confusing ("classical liberal"), or lacking in any positive connotations ("minarchist," etc.).
Regarding David's suggestion of "free exchange," I think it's clever, but has several shortcomings. Most important, many of the freedoms defended by libertarians do not involve any kind of exchange. Moreover, the term is more awkward and has fewer positive connotations than libertarianism. Indeed, for many people, the word "exchange" may conjure up negative images of evil capitalists or scam artists.
Libertarians today face many daunting obstacles, but I don't think that the need for a new name is one of them. The one we have is perfectly fine, especially compared to the available alternatives.
UPDATE: David e-mails:
I didn't say libertarians shouldn't call themselves libertarians. I was raising the question of what a libertarian should say when asked what he believes in. "Liberty," in my view, doesn't quite cut it, nor, as I blogged, do individualism, classical liberalism, etc.
I apologize for misinterpreting his post. I think the misunderstanding arose from the fact that most of the terms he discussed (e.g. - classical liberalism, market liberalism, etc.) are usually thought of as substitutes for the term "libertarianism" rather than as explanations of its meaning.
Nonetheless, I think most of my original points stand, to the extent that they were directed at the general debate over what libertarians should call themselves rather than at David's arguments specifically. Regarding the term "free exchange," I think most of my reservations about it apply even if it is used only in the way David envisions. If I had to come up with a short explanatory phrase about what libertarianism means, I would prefer something like "maximizing liberty" or "minimizing the power of government." Obviously, these would require explanation in order to apply to particular issues (and even libertarians will disagree about the applications among themselves). But the same is true of any brief phrase - as David pointed out in his original post.