I think that having double blind experiments are beneficial in their way since it reduces the possibility of a bias from both the subject and the administrator. This ensures that the results read in by the administrator is not tainted or affected by assumptions or expectations made. In this way, only the observations or the effects that manifest will be the only true result for a test. This will truly show if the results are valid and if the product really works. It is not necessary but it would be a good way to conduct an experiment. However, it is difficult to run due to the coordination that must take place to make sure that the unknowns are kept that way.