Sorry, my tone was way out of line. I think each of the three methods (though AO is not a true shadow) has merits. I agree that raytrace shadows are awesome and versatile. I don't think that they're the "end all, be all" shadow types, and should be evaluated on a shot by shot or project by project basis.

Before PRman had raytracing, those functions would be carried out by BMRT though very sophisticated message passing, but it was only used when absolutely crucial to the shot. Also I believe ILM uses mental ray not because of raytracing but due to certain PRman limitations such as rendering dielectrics very close to the camera, etc.