(With the obvious exceptions for things like verbal agreements to transfer ownership in land, unconscionable terms, agreements obtained by coercion, and so on.)
...and we're back to 'you don't own what's in my brain'
Are you arguing that copyright and patent terms are not just unfair or unreasonable but *unconscionable*? Are you saying I should not be permitted to sell you a CD on the condition that you do not copy it?
It is a fundamental Libertarian notion that the government should never prevent two consenting people from making a mutually-beneficial agreement without an extremely powerful justification for doing so. I don't see an extremely powerful justification for prohibiting agreements of this kind.