I hate to disagree with your reasoning, Ed, but I do. Astronaut bootprints and otherwise disturbed soils only appeared dark in the immediate vicinity of the LMs, where the descent engine plumes had swept loose dust from the surface and brightened it. Every LM landing site imaged by the J-mission pancams showed a brightened "splash patch" of soil extending 50 or so meters out from the actual landing points.
Extensive review of the TV and film record, and accounts of the astronauts' impressions on the scene, confirm that footprints, rover tracks, etc., did not generally darken the soils at any reasonable distance from the LMs. In fact, in some places (especially at highland sites), footprints and other soil disturbances actually brightened the soil, since in some areas a dark gray surface covered brighter deposits.
That said, some hardware impact sites that have been imaged do display dark rays -- notably some of the S-IVB craters. I've wondered if that might not have something to do with the composition of the impactors, however...
-the other Doug