[Eugenia Gabrielov]

Sub-team necessity truly depends on the team. More often than not, having sub-teams is a huge help on a large team because it keeps things moving and separates the group a bit by interest. That way smaller groups are fullfilling goals and completing tasks based on one focus, and it also contributes to consistency.

On the other hand, if your team is fine without subteams, and you don't think it could be improved with that added organization then you should refine your own method of doing things. Just keep in mind that as you grow, the free for all attitude becomes a lot more difficult to maintain.