The story said the SEC asked for a waiver so they could experiment with this.
A possible drawback is that you may not know who is standing near you and you could say something that you would normally say in a crew huddle with some privacy but which you would not have in this situation. Also, unless it is a pretty sophisticated system, someone can find a way to intercept the communication and maybe not everything said between the crewmembers is something they would like heard. If there was strict radio discipline, these issues might be contained.