I think you really have to have a central vocalist, it's crucial to most popular genres. Take rap for example, often times it's just live vocals over a recorded backing track, and that's good enough to fill a large venue. I just think there should be an understanding going in that it's the vocalist's show. Bands have names like "Smashing Pumpkins", giving the idea that the vocalist is just one of the many, when obviously that aint so, and then you have band names like "Neil Young and Crazyhorse" and then at least it's baked in to everyone's mind that the vocalist and the backing band are not really one and the same. It should probably always be that way, and the backing band should be asking "whats in it for us?" apart from the lead singer and whatever it is they're in it for.