It depends on the aim or purpose of the band. If the idea is for a bunch of friends to enjoy themselves making music, a democracy is fine. However, if the aim is more business-like, then someone needs to have at least a casting vote of some sort or nothing gets done. Degree of input counts, too. If someone provides an expensive PA or gets bookings, in addition to the contributions they make to playing, arranging, etc that should count for something when decisions are made.