A libertarian paradox?

[Citizen James]

How much power should the government have to prevent people from infringing on other people's rights?

Assume for a moment that entities other than governments (people, corporations) can infringe on the rights of others.  That may be hard for some who follow libertarianism as a religious dogma rather than a philosophy (and who, I would argue, are actually somewhat authoritarian in their worldview).

Beyond the obvious (such as kidnapping, murder, and theft) what should people be allowed to do to one another.  Can a person sell themselves into indentured servitude, or even slavery?  Could they do the same with their kids.  Would it be acceptable for companies to set up their own towns where their rules take precedence; could an employee, say, be locked up indefinitely without trial if they had previously signed a waiver as part of an employment contract.  Would it be acceptable to coerce someone into de facto servitude - say an exchange of indentured servitude for life, for life saving medical care for their child.

It is odd as I see two varieties of Libertarian out there - one brand which has a rather positive view of human nature - that most people are, to use a phrase I heard once, responsible enough to be trusted with matches (or their own decisions).  Laws exist to deal with the sociopaths and similar exceptions.  I would suspect that this type would consider the government primarily as a device to ensure individual freedom.    The other group is more nebulous, but tends to have a darker view.  Call them Randroid, or kleptocrat, or just plain crazy/evil - they tend to have a more negative view and believe that it is normal (or even desirable) for one person to exploit another.  Needless to say, they tend to fantasize themselves the exploiter, rather than the exploited - perhaps in part due to a Gaultesque overestimation of self-worth.  Their philosophy strikes me as really more authoritarian - in which they imagine themselves mighty leaders over the lesser peoples they command.