Please consider a llDetectedPrims() call, similar to the llGetNumberOfPrims() call we are getting in 1.5, but returns the number of prims in an object/set detected by a sensor.
This would help landlords somewhat, of course not as good as the suggestion in Nexus Nash' "Land Objects" thread.
But at least they could run a sensor and get a quick number of prims in the immediate area.