I would argue that capitalistic property is nothing more than "legal privilege" or an artificial arrangement imposed by arbitrary violence. Usufructuary property is just what Thomas Hodgskin called "natural property," whereas capitalistic property is "artificial property." In any primitive society, usufructuary or possessory rights will naturally develop according to custom. Capitalistic property requires legal institutions, systems of enforcement, and violence.

If I acquire property, my possession of it naturally dictates my control of it. So, since I possess it, I can sell it. This is usufruct or possession. Capitalistic property is a legal arrangement that differs slightly. Capitalistic property isn't linked to possession (which is natural) but to title (which is artificial). Thus, I can own a title to a piece of land, and that title (an artificial document) is what makes me the owner. Thus, my ownership under capitalism is predicated on artificial legal arrangements. And this artificial property is in contrast to natural property. If there is abandoned and vacant land, under capitalism I cannot just homestead it, because someone else has the title even if they are not occupying or using the land—they have ownership even though they don't have possession. So, capitalistic property is kind of statist in the first place, being based on arbitrary legal titles/deeds rather than on natural rights. And capitalistic property rights can only be upheld by arbitrary aggression against non-aggressors. If a person walks on to a vacant/abandoned plot of land and tries to homestead it, the owner will call the police and have the man forcibly removed. So capitalistic property is based on the violation of the Non-Aggression Principle.

Furthermore, this sort of property leads to inequality and hierarchy. Land is currently monopolized. You can't just homestead land anymore, since every inch of land is claimed by someone. Most of the land isn't in use, so it is really in a state of nature—and you ought to be able to homestead it and claim it as your own. However, artificial titles are enforced by an authoritarian system of law and law-enforcement. Anarcho-capitalism wants privatized law and law-enforcement, but they still want the arbitrary and authoritarian system of legal privilege in regards to property titles. So anarcho-capitalism can be seen almost as advocating privatized statism instead of being on par with individualist anarchism.

Also, capitalistic property leads to wage-slavery. Once all the land is owned, there's a quasi-monopoly situation. So, some people have land and productive property and others don't. You wind up with haves and have-nots. Then you end up with a class of rentiers (landlords/capitalists) vs. a class of proletarians/wage-laborers. The one class rules over the other as bosses. The average man has little choice, being dispossessed, to do anything but sell himself as a wage-laborer to some capitalist. Sure, he can choose his employer, but that's just choosing a master, not enjoying real freedom.

If you want to read more on the property issue and the reasoning behind refusing to classify anarcho-capitalists as anarchists, you can check out my article on Proudhon's "Property is Theft": http://www.anarchistsocialdemocracy.com/pdf%20Documents/Property%20is%20Theft,%20Property%20is%20Liberty.pdf