Clearly defined roles and responsibilities are essential.
At one startup I worked for, there was a time when we asked the VP of Product Management to also serve as VP of Engineering — we'd lost our Engineering leader and filling the role was taking a long time.
With no disrespect for the people involved at the time, here's why that wasn't a great idea.
There must be a healthy tension between those two roles. Engineering needs firm, unambiguous requirements. And Product Management needs those requirements fully met and the product delivered on budget and on time.
When one person holds both roles, accountability disappears. It's too easy for the engineer to forgive incomplete requirements when the engineer is also the overworked product manager. It's too easy for the product manager to forgive schedule slips when the product manager is also the overworked engineer.
The same applies to Engineering and Manufacturing. If the head of Manufacturing is also the head of Engineering being graded on finishing on time, it's too easy to declare the product "done" before it's truly ready for production.
You're on the same team, but the person throwing the football shouldn't also be catching it.
At the earliest stages, everyone wears multiple hats — that's unavoidable. But as the company grows, the founder needs to formalize clear handoffs. VP Engineering holds the PM's feet to the fire. VP Ops holds Engineering's feet to the fire.
Good corporate hygiene requires well-defined roles and responsibilities, with a champion in each seat who owns the outcome.