Most of the bands I've been in have been democracies, though they do tend to have members who will tend to lead and others who will tend to follow. I think I've only been in two bands with self-appointed leaders. No problems with playing what I wanted to play but there was a degree of personal friction with one (who sacked me) and the most recent one I decided I'd had enough of supplying the PA (mutually agreed separation). I prefer the democratic model as long as there aren't any rogue members - with one band, the guitarist simply didn't learn any songs that he didn't particularly fancy doing, even though they'd been agreed. Plus there should be a limited ability to veto a song. I don't really want to play "All Right Now" but the others do, so I simply refuse to play during the verse.