Well the thing is Reiki is based on Ki(or Chi) energy, which is basically only "life force" energy. Such energy(from what I understand) doesn't really possess any penetrative power to begin with, its merely energy to sustain ones health. Its not "evolved" into higher forms of energy, and thus any dormant supernormal abilities inherent within the human body cannot be activated within the practice of Reiki. Thats why beyond the level of healing and fitness, Reiki is of very little use.

As I said, I know personally former practitioners of Reiki and even they themselves told me that the energies developed in Reiki aren't very substantial and are quite limited.