Placebos, used ethically, are powerful tools. They can cure diseases, make food taste better and dramatically increase the perceived quality of art. They can improve the way teachers teach, students learn and we judge our own safety.
Not all placebos work, and they don't function in all fields. Here are some things that successful placebos have in common:
They do best when they improve something that is difficult to measure objectively.
Does this stereo sound better than that one? Is your headache better today than it was yesterday? How annoying was it to wait for the bus in this new bus shelter?
Sometimes the outcome is difficult to measure objectively because it's abstract, but sometimes it's because it's personal.
If you claim that a new driver makes a golf ball go further, a simple double-blind test is enough for me to know if your claim is legitimate, and if it's not proven, it's significantly harder for me to buy in, which of course is the key to the placebo effect working.
If I tell a teacher something about his students, and that knowledge causes the teacher to take a more confident approach, test scores will go up. But what the placebo did was change the teacher (hard to measure), which, by extension, changed the test scores.
Straining credulity is a real danger, one that denudes the effect of placebos.
In 1796, when homeopathy was first developed, we knew very little about atoms, molecules and the scientific method. As a result, the idea behind these potions was sufficiently sciencey that it permitted many people to convince themselves to become better. Today, informed patients find it can't possibly work, so it doesn't. The same thing is true for astrology, which was 'invented' before Copernicus.
Twenty years ago, audiophiles actually paid $495 for a digital alarm clock that made their stereos sound better. It faded fast, mostly because it was embarassing to admit you'd bought ridiculous magic beans like these. But today, $100 usb cables continue to be sold, because, maybe, just maybe, something is going on here. We're not sure we actually know enough about dielectrics and the skin effect to be sure.
Argue all you want about whether or not you want to be buying or selling placebos, but it's quite likely that the right placebo with the right story can dramatically increase certain outcomes.
If you want to improve performance, the right placebo is often the safest and cheapest way to do so. The opportunity is to find one that's likely to work, and to market it in a way that's ethical and effective.