At what point in a team’s growth must process change drastically? A lone coder can get away with source control and a brain. A team trying to ship large prepackaged software to local and international markets must have a bit more in place.
If you’ve experienced a large transition in ‘process’: Was the team’s process successfully changed with the current members or was the team itself mostly replaced by the time the process change came? What were the important aspects that changed, were some unnecessary?
In my experience this transition occurs at exactly the moment at which you also need management. It is hard to get above 8 developers without some over-arching coordinating function being in place, whether it is a team lead, segregation of tasks or old fashioned management. The reality I have witnessed is that even with the best, most talented, most bought-in developers you still need coordination when you get above 8 working concurrently.
And there is a discontinuous step in process as you cross that boundary. However it needn’t be catastrophic. The best approach is for the team to adopt as much formal process as it can when still small so that all the necessary behaviour and infrastructure is in place. I would argue that this is synonymous with good development in any case, so even the lone developer ought to have it (source code control, unit tests and coding standards are all examples of what I am talking about). If you take this approach then the step up in process when it occurs is not so much a jolt as a rigorous coordination.
Every developer you add need to be brought in with the process already in place. When you get to 8 (or whatever the number turns out being for you) then you’ll find that your team meetings get a little too loose and wordy, personalities start playing a part and it is more effective to divide activity up. At that moment your boss (or you if you are the boss) will need to appoint one or more coordinators to distribute and control work.
This process (should) scales up as well if you stick to your processes. Teams can sub-divide or you can bud teams out to perform functional tasks if necessary. This approach also works regardless of the methodology you have chosen for your project management, be it Agile or not.
Once you get up to 4 or 5 teams, i.e. 30-50 people then you will almost certainly need people who are happy that their sole task is coordination.
If you are small now and contemplating or expecting the complexity shift, then make sure you get your fundamental processes nailed down immediately and certainly before you start adding more staff.
HTH and good luck