Band leader is a must!
The band leader must know when to be the boss and when to be a friend.
I have been band leader in a few bands. In my bands, we work decmocratically off stage and in the studio but on stage, someone has to call the shots to keep things smooth - otherwise it would all be a big mess. Argue or debate or discuss all you want off stage but on stage the leader calls the shots, especially when you are doing long sets and you call out tunes to suit the occassion / venue. A leader must know how to "read" the crowd.
Being a leader does not necessarily mean being a dictator. I delegate other band duties (e.g downloading songs, burning cds, equipt details, transportation logistics etc) to other members while I handle trade enquiries, quotation, our blogsite etc. However, we do have a vote system in my band where we vote on all issues. Majority wins.
The band leader must also be the back bone of the group - e.g in band competitions or gigs - to inspire confidence to his band mates, to drive them to greater heights.
My 2 cents on band leadership.