You asked for my opinion on this... honestly I am quite a bit out of my depth here.
I think one should be cautious about attaching the Holographic principle to everyday objects. The basic principle only works (I think) when applied to ``topologically natural boundaries'', which usually mean light-cones or event horizons, or the like. The principle states that all the information necessary to interact with one of these holographic bodies must be encoded on the surface.
This does suggest that the essence of everything is 2D, but I don't think it precludes the existence of 3D - we need 3D space to have 2D surfaces. I think the holographic principle reduces things to ``bubbles'' - i.e. anything important about the contents of a bubble needs to be projected on the surface, so one could equally validly treat the surface of the bubble as the real thing and say it contained nothing.
But, on the other hand, you (or I) are obviously
not topologically natural objects, our boundaries are not related to space-time curvature. And on a more fundamental level, electrons in a crystal (silicon, copper, etc.) are defined by 5 quantities: the energy (or band index), three components of crystal momentum, and their spin. You can't project a 3D crystal momentum onto a 2D surface without losing information - and yet the information about electrons in a crystal lattice is readily available by a number of experimental techniques.
I suppose one could argue that the subatomic particles (electrons, quarks, etc.) that make up macroscopic objects are the 2D bubbles, but there isn't much gained by that in my opinion.
I worry that the Holographic principle comes from an attempt to resolve contradictions between the interactions of quantum objects in classical fields - in particular classical fields that are plausibly near a quantum limit (like an event horizon could conceivably be) - when a better approach might be to properly quantize the fields first (of course there hasn't been any success with that yet).
I admit that I am fairly biased in this sort of discussion. I am an experimental physicist, and in particular I study condensed matter and materials. In my opinion, lots of theorists provide lofty philosophies that are based on large, weakly interacting systems (like black holes treated as a single object floating in interstellar space) or very small,
discretely interacting systems (like subatomic particles colliding once or twice in an accelerator).
In my opinion, theorists rarely talk about the ramifications of the theories they construct in those settings on
real life, i.e. millions of
continually, and
strongly interacting particles (like electrons in a solid). A black hole in space, or a relativistic particle in an accelerator can have definite surfaces (light cones, event horizons, whatever) - that exist on
all length scales. But the surface of an object is very dependent on the scale you are measuring.
In terms of the holographic principle, what is the surface of your body? It probably looks pretty clear to you right now, but if you studied your skin at a micron scale it would look a lot more like a sponge, and on a nanometre scale not only would it be full of holes, you'd have a hard time telling what part was your skin and what part was the atmosphere around you.
The difference between volume and surface is pretty clear-cut for a perfect sphere. What is the difference in a
fractal?