Libertarianism is, in an odd sort of way, like communism. Both look good on paper, yet neither is practical.
You don't think so? Well, what about these concerns:
For libertarianism to sustain itself, it would require a guaranteed, eternal majority. This will not happen or, at best, it will only happen during short runs. People, being people, will use their free will and shoot libertarianism out of the sky.
It might work with an iron first under a benevolent dictator. But there are two problems with that. One, we see how that has worked for communism, and two, that also would rely on an eternal march of benevolent dictators. That won't happen either, and, further, would actually mock libertarianism.
Then there's the business of freedom. Libertarians preach it with an almost religious fervor. It's their end-all be-all. But 'I'm for freedom' isn't really a tenable position. It begs an entire litany of questions, not the least of which are questions like, freedom to do what, freedom to be what, and whether what we want are things we ought to want. Libertarians forget, or refuse to accept, that freedom is only a means. It is not an end. That is, unless you want total, complete freedom to do absolutely anything you want. To be sure, they don't believe that. They believe there are some limitations on human behavior. But note that that means they aren't actually in favor of freedom anyway because they do, when it suits them, restrict it.
Next there's the matter of how they might get their agenda in place. In the United States today that cannot happen except through revolution or politics. Yet they abhor politics and politicians, and even should they approve of a revolution (which would be dangerous as such things tend towards going out of control) and perhaps a contradiction within their philosophy. How can you force people to become libertarians against their will? You can't, outside of confessing that freedom is not without bounds. Unless, again, and we love hammering this point home, you don't believe in unfettered liberty.
At the end of the day, libertarian philosophy contradicts itself. We believe that is evident in the above comments. You simply cannot preach freedom as an end and then argue that it can be restricted in any way, shape, or form.
They sound good and they look good. Yet all they do is bang an empty drum.