@jlou he does make quike a compelling case with the respsonsibility thing, i like it! i'm not quote sure yet how much that really gets you. but i'll have to think about that more.
one thing it seems that i disagree with Ellerman (and most ancaps) is the whole "labour theory of property" thing, which i came up myself as a derogatory term.
basically what you do to an unowned thing has subjective value, and there can be legitimate disagreement on whether you "mixed in your labour" or ruined it.