That last one may not sound like social control - and it isn't, when all parties involved (and not just the contracting ones) have symmetrical information, and (nearly) equal power. You can surely contract with your supermarket over Kraft Dinner without control being a major issue, but there are many places where these conditions are not met.
For example, there's a classic ethical dilemma that goes like this: Mr. Smith's wife is dying of a terrible illness. The pharmacist has a drug that would save her life, but refuses to sell it to Smith at a price that he can afford. Smith pleads and wheedles, and tries to negotiate barters or extended terms of payment to no avail, and resorts to stealing the drug to save his wife's life. Were his actions correct?
Those with moderately advanced moral reasoning, researchers claim, see Smith as justified in his action, as a human life is a higher good than mere possession of objects; the demands of saving a life outweigh the demands of protecting property.
Pure libertarianism fails this test. The libertarian would construe attempts to compel the pharmacist to offer the drug at an affordable price as a form of taxation that impinges on freely chosen action. In doing so it holds contracts to be more important than the very lives of the people who would hold them.
This placement of abstract rules above human life and suffering puts it in a league with doctrinaire communism. As much as it would be nice to believe that we are all islands, connected only by the contracts that we choose, this is just as wrong as believing that we are nothing more than a component in a collective. It shouldn't be rocket science, but libertarians seem and communists alike tend to forget that basic humanity requires we take an interest in the welfare of our fellow travelers, weighting carefully the complex trade offs between personal and collective interests. There may be ironclad cases to be made for each pole (person and collective), but sometimes ironclads clash, and we have to put aside the pleasures of dogmatic certainty in favor of pragmatic balances.
But there is a greater rub still: Libertarianism is a self defeating system. It may only fail badly when there are extreme power imbalances (say, between a South American villager, and a multinational corporation who dumps toxins into his drinking water as a side effect of producing goods it profitably sells to Europeans), but, if run long enough, will create these power gaps, even where they didn't exist before.
Unfettered laissez faire capitalism tends to be good at creating wealth, but lousy at distributing it. The turn of the 19th century (and to a lesser extent, the Bush years) saw turns towards libertopian economic freedom. It saw enormous wealth disparities created, with robber barons hoarding vast amounts of wealth, and the poor becoming poorer. A rich person has many options in a negotiation that a poor person does not. Only one of them can be placed in a position of NEEDING the other, for a job that provides food and shelter and care for vulnerable relatives. And when only one party needs the other, you have the very definition of a strongly power imbalanced negotiation that invites abuse.
Lest you think I'm making this up, on this great page of libertarian-relevant quotes, there is the following gem:
23- And God saw everything he had made, and he saw that it was very good; and God said, It just goes to show Me what the private sector can accomplish. With a lot of fool regulations this could have taken billions of years.I assume that God is the merchant here. Now think about the powers involved. God: infinite. Us: not so much. God, as a good capitalist, should try to get the best possible terms She can. If She can make us give up everything we have for free, that would be entirely rational... And let's face it, She pretty much could. If God is a libertarian then we are all very much screwed.
Footnote: Now even Bill Kristol is down on the Libertopian vision. Yes, THE Bill Kristol I was mocking just a few posts back. Reality has come a little loose, my head hurts.