[emerongi]

I'd say that in very small teams (up to 6 people), it's better to not have a certain leader. Someone will become more dominant in the group anyways (usually a person whom everyone trusts and likes). In big teams, it's hard to get anything done without someone set to lead it.

[armed10]

I think you're right. In my personal experience I've found that in most small teams, there are few who want to lead. If you have mature members, this becomes less of a problem. However, I still find diffusion of responsibility a common theme in small teams, appointing a leader to absolve them from any personal responsibility.

Combining a "more dominant someone" with atomic responsibility is probably the best way to go with small teams.