Well, I'm certain this has been discussed before, but I'll weigh in with my thoughts.
In the back, wheel backspacing for a live axle style is just user preference. Lots of backspacing, neutral backspacing, etc. just doesn't matter that much. Reducing strain on the bearings via neutral backspacing isn't such a bad idea.
In the front is where the discussion gets interesting. Ideally, the wheel should be set up such that scrub radius (the difference between the pivot point established by the ball joint centerlines, and the center of the tire contact patch) is less than an inch. Modern suspensions with a KPI of 8-14 degrees usually need a wheel with a significant backspace. My clean sheet of paper design for my car used an 18x9 wheel with 7.375" of backspacing. Have a look at modern cars with oem wheels and you'll find that nearly all of them have "flat" wheels (not much exposed lip) for this reason.
For a brief discussion of this have a look
here.
jp