I think that placebo controlled studies are ethical and also very important in clinical trials. Placebo studies are important to the study because they can be compared to the results of the drug and without any other factors differing besides the drug show the true difference that the drug makes, if it makes any at all. From an ethical standpoint it may seem unethical for certain subject suffering from the same disorder as the other subjects to be given the placebo instead of the actual drug, but subjects are warned of this beforehand.