I think that playing with form can be very risky, but if done well, it can be far more impressive than staying within the normal bounds of form. The Pentatonix is an example of a group that has altered the traditional form because their songs lack instruments entirely. They rely completely on singing and themselves to create background music and audio. Their attempts are successful and they make a lot of very impressive music.They broke away from the traditional idea that songs need music and instead they make their own music to base on.
Oh my goodness, that is a great and unique example. I remember Mrs. Kubly playing some of their songs for us in elementary music class. I always appreciated the break from tradition as it was more impressive like you said.
My mother raised me on Pentatonix, especially around Christmas time. I remember being really into the idea of people creating music just by themselves.