If you can do a thing ethically, calling your act an experiment, or paying attention to how people react, doesn't create an additional ethical burden.
It doesn't follow that if doing X doesn't make anyone worse off, we should allow X. This fails to consider the impact of incentives. It may be that if we permit X, X would be better for everyone in the current situation, but permitting X also affects the balance of what situations exist to begin with, leading to everyone being worse off overall.
Is the harm that the average ethical review board prevents less than the harm that they cause by preventing research from happening? Are principles such as requiring informed consent from all research participants justifiable from an utilitarian perspective?