Take a stroll through the clinical descriptions of some common medicines and see how often you see this phrase: "The exact mechanism of X is unknown, however..

Take a stroll through the clinical descriptions of some common medicines and see how often you see this phrase: "The exact mechanism of X is unknown, however..." It's kind of frightening. (two off the top of my head: http://www.drugs.com/pro/klonopin.html http://www.drugs.com/pro/klonopin.html & http://www.drugs.com/pro/prozac-capsules.html http://www.drugs.com/pro/prozac-capsules.html)