[evanb]

For radiation, yes.

But for force laws, having a massless carrier is critical for an inverse-square law. With massive carriers (like the carriers of the weak force, W+Z bosons) the range of the force scales like 1/M; the force law is more like exp(-Mr)/r ---> 1/r as M-->0. The diminishing of the force with exp(-Mr) means flux isn't conserved. (note I worked in units where hbar = 1 = c, so that the W's mass ~= 80 GeV/c^2 corresponds to 1/M << 1 fm)

[philzook]

But also things that aren't radiation or high energy physics. Inverse square laws are ubiquitous in hydrodynamics, heat flow, electrostatics. Good ole fashioned 19th century physics. And I think that's its most natural arena.