Not a scam, One of my lecurers who is a leading exercise physiologist and hardcore endurance junky uses them when training his athletes as a flow constrictor to decrease repitory output and improve performance. You can also get ones that you put lime crystals in and they can simulate altitude by absorbing some of the oxygen and reducing the oxygen concentration that you breath in. I have tried one and it seemed pretty uncomfortable and I dont think it would be that user friendly but if this guy uses them then they cant be altogether useless.
