If a drug trial reveals that patients receiving the drug did not get any healthier than those who took a placebo, is this a failure?  It depends what the alternative treatment is.  Implicitly its a failure if we believe that doctors will prescribe a placebo rather than the drug.  Of course they don’t do that (often) but we can think of the placebo as representing the next-best alternative treatment.

But the right question is not whether the drug does better than the next-best alternative, but instead whether the drug plus the alternatives does better than just the alternatives.  It could happen that the drug by itself does no better than placebo because the placebo effect is strong, but the drug offers an independent effect that is just as strong.

If so, then the right way to do placebo trials is to give one group a placebo and another group the placebo plus the drug being tested.  The problem here is that the placebo group would know they are getting placebo which presumably diminishes its effect.  So instead we use four groups:  drug only, placebo only, drug plus placebo, two placebos.

Maybe this is done already.

Followup: Thanks to some great commenters I thought a little more about this.  Here is another way to see the problem.  Conceivably there may be a complementarity between the placebo effect (whatever causes it) and the physiological effect of the drug.  The more you believe the drug will be effective the more effective it is.  Standard placebo controls limit how much of this complementarity can be studied.

In particular, let p be the probability you think you are taking an effective drug.  Your treatment can be summarized by your belief p and whether or not you get the drug.  Standard placebo controls compare the treatment (p=0.5, yes) vs. (p=0.5, no).  But what we really want to know is the comparison of (p=1, yes) and the next-best alternative.  If there is a complementarity between the placebo effect and the physiological effect then (p=1, yes) is better than (p=0.5, yes).