It depends on the terrain.
In Wyoming hunting antelope that would be way too close.
In thick eastern whitetail country you could have 4 people set up across 150 yards in certain situations.
You need to look at the terrain and make the decision for yourself. If you're sitting there staring at each other, it's probably too close for a firearms hunt. Although not in every situation. If your bow hunting a field edge, again... you could have people set up every 50 yards and be alright.
Safety needs to be your #1 consideration.
-Jake