[csmatt]

Does the increase in radio receivers require an increase in the energy to broadcast to the same area?

[acjohnson55]

Nope. If it were inductive or capacitive transmission, this would be the case, but for far-field radiation, it's generally not.

[josh2600]

It's more Shannon-Hartley: http://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem (I think).