To offer an opinion against their use......
From a racking safety point of view, I have found that they COULD potentially be dangerous. The operators will tend to use them as a means of knowing when they are in the proper distance by going in until they hit the backstop. When they do this they are pushing against the rack, and could, underline COULD, cause damage or ultimately cause the rack to overturn.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.