The biggest one is not having the VPs in place. If you don’t have all the core VPs in place by $4m-$5m in ARR, then hiring and scaling slows way down in those functional area without one.
The second biggest is lack of redundancy. You lose one great engineer, your top salesperson, your lead marketer … and that functional area takes a huge hit.
But get to $10m or so, and the cavalry comes. You get some redundancy, some more help, and a full management team by then.