Palmetto Proving Grounds

IMO, it's about creating a little more room for "quick hitter" type runs and passes from a position where the QB isn't under center, nor in a full "shotgun" formation. If DL is getting some decent penetration, if the handoff and timing is right, defenders don't have as much time to get set and react to something that happens farther from the LOS if you're in the "gun." Also, just a "feeling" thing for offensive staffs, and sometimes, simply just a different look to try to keep the D off balance.

shotgun for passing and yet the runnning back is still directly behind the QB therefore able to run to each side equally. Also you can do play action and the QB does not have to turn his back on the entire defense just one side.

I dunno if that link is working but....

I dunno. Says it here too.