It is bad to introduce too much process too early, and a good measure of when you need it is when the pain of not having it exceeds the pain of the process. I really dislike unnecessary process, but as you grow different processes become necessary and they make life easier and more predictable.
It isn't rare to have the wild west at a startup in the early days and it isn't rare to lose a few people when you start putting in necessary processes because they don't want the constraints. One of the most valuable lessons I have learned over the years is that it is healthy when people leave that aren't on the same growth path or maturity of the organization. Don't fight to keep people when this is the case, it just adds stress to the organization and people internally know that the person isn't a good fit anymore. So let them go. Hard thing to do sometimes, but necessary as companies grow and mature.