I have a hard time referring to myself as ancap but I tend to agree most with what they have to say. One area I disagree with them on however is the concept of land property and its permanence, as opposed to other forms of capital which can be abandoned. This is the major flaw in Rothbard's thinking in my opinion. If you can abandon a shovel on the side of the road, why can't you abandon the land itself?
I think he drew this distinction in order to avoid the then arbitrary task of defining when exactly someone might abandon their land, but in so doing he made an arbitrary distinction between different forms of property. Land can indeed be abandoned and our concern should be with defining when that quality has occurred, not with protecting the rights of people who have neglected their property to such a great extent.
The reason I think that property needs to exist however is because of the nature of philosophy and the systems we construct using it. Philosophy as it pertains to governance is exclusively centered on the problem of how humans should interact with one another. As such, it must consider some way of respecting the boundaries of a person's physical body and the products of their labor. Without this, society can't exist at all. In fact, no biological creature can survive without at least carving this out of nature for itself. A philosophy of governance is about mutually respecting that need in your fellow human beings and systematically encoding it into a set of just rules. I can't see a practical way around private property ownership if we're to achieve this.