Back to AdS/CFT. Which theory represents spacetime accurately? The target metric in string theory (or at least a non-compactified version) plays a pretty traditional role in spacetime.

CFTs are invariant under conformal transformations of the metric.  This means that the thing that might represent ST is the equivalence class of metric conformally equivalent to Minkowski.

Does a spacetime with only conformal structure even represent spacetime? No inertial structure. Geodesics, even, are not invariant under conformal transforms.  Thus the structure is not a candidate for representing phenomenological spacetime.

Giant insects!?  [any notion of being larger or smaller at stake]

Brian Pitts: Are these the same point? If nothing were massive, conformal structure would be all we need.

EK: Sure, but not exactly the same point.