Suppose it turned out that for a private law based, anarchocapitalistic society to work effectivelly, it was necessary for people who shared the same legal system to live near each other. Ideally we would want people to be able to choose their legal system independent of where they live, but suppose that this just doesn't turn out to be practical. You can still choose your legal system, but you have to move.
This is plausible especially if the main things that most people want to be illegal represent physical acts; it is likely to be easier to limit physical actions within a specified region than to try to do so on a place-by-place basis in discontinuous households and business enclaves spread around the world. It is a matter of efficiency, and the conflict between the idealized world we would like to live in, and the balky, stubborn world of physical reality.
I don't think this would be a fundamental revision to the ideals of anarchocapitalism. Moving is a pain, but assuming that most people don't change their legal system very often, the costs would not be too bad. You would still have the essential element of choice of laws.
Imagine, in contrast, a miniarchy which allows people and regions to peacably secede at will. Governments of today seek territory above all else, but if we suppose that minimal legal systems can be accepted, then perhaps the principle of allowing people to secede will also be acceptable. Justice would arguably require allowing people to leave and not forcing them to continue to live under the local laws.
Aren't these two systems the same? What would be the difference between a world of competing miniarchies and an anarchocapitalist world where people's choice of law determines where they live?
It seems to me that these two approaches are fundamentally compatible, and both represent a common vision for a world where people have much more choice and flexibility in their laws than they have today.