For snake oil to work there's usually a happy customer (shill) harking the benefits in front of a crowd. The shill is always in on the act. Are we to say that people who have tried it and agree that there is a positive effect are in on it? Or that they are under the effect of placebo? Or that they have the taste of the Philistines?
Forums like this and other sites routinely audition products and word gets out that something does or doesn't work. Eventually there comes a consensus. That is sometimes followed by testing by both camps (those who believe and those who don't) who still insist that they are correct and the other is mad, delusional or intentionally misleading.
Then we stumble upon a site where it has all been tested and analyzed six ways to Sunday with assorted graphs and readouts and low and behold, there are still some who refuse to accept it. Or minimize its effects. Or dismiss it out of hand, and lie in wait for the next claim to pop up. The results can prove or disprove but no amount of persuasion works.
Rinse.
Spin. (no pun intended)
Repeat.
My only point is that some products do have a beneficial effect, albeit slight or plainly evident, and some are as worthless as the space I take to write this. I only to point out the lengths people go to to further their beliefs, truth be damned, when all they have to do is listen for themselves, or examine the reviews and tests of those who have.
Beliefs, and the emotions that accompany them, are the hardest to overcome.