Security keeps that area clear - the people who sit in the front rows have paid TOP dollar - for an unrestricted view..... you can stand at the seat assigned to you - no problem (no aisle standing inside the reserved area - safety) At least this is how it was last year.
Last year we had front row Gold Circle on the left side of the stage, and we were allowed to stand (we also ok'd it with the folks behind us). The only problem with those seats, is that there were about 20+ people standing in front of us. There wasn't enough security to keep the other Gold Circlers at their seats. So essentially our front row became 5th or 6th row. Could be why Gold circle seats are now only center stage.