Interesting thread, one with differing strong opinions. I've partial to mine, but after reading all the comments it seems (like a lot of other things in freediviing) that proper buddy distance has a lot to do with the conditions we dive in and the particular kind of diving we are doing.
I'm lucky, the Bahamian water is very clear. We shot slings and are no longer intensively competitive about the biggest, most fish. I have been through a lot of stages in buddy system, from "whats a buddy", to same ocean, to now when I can see my buddy all the time, working one up one down, and we don't get very far away from each other, There's no reason to. The boat is following us and we work together on the fish. Having a set of eyes above the shooter is often critical to following fish swimming in and out of ledges. Separating makes it hard on the boat driver and definately increases shark problems. Teamwork, in my waters, makes for more fish in the boat, is just more fun, and, if anyone did have a bo(I've seen one), we could deal with it easily.
Under other conditions or types of diving, this type of system might get pretty difficult, but It seems like the closer a diver could come to it , the better it would be.
Connor