Whenever I hear people or politico's say 30 round magazine is not necessary, I think about a guy like Reginald Denny during the LA riots. He could of used one or two in my opinion.
Reginald Denny isn't the best example on this point. First, it injects a racial component into the discussion that isn't helpful.
But mainly, it's not really on-point, because Denny wasn't a case of running out of ammo. Denny didn't even have a gun at all.