As a full scale pilot with a commercial license, I can tell you that over congested areas, a pilot legally (FAR 91.119,b) has to be at an altitude of at least 1,000 feet above the highest obstacle within a 2,000 feet horizontal radius of the aircraft at all times, unless it is some type of waivered operation like what I do in my pipeline patrol flying. Aerobatics does not qualify as a waivered operation unless it's being conducted at some type of airshow or contest, and then only in designated areas. There is another rule in the Federal Aviation Regulations that deals with aerobatics and where they may be conducted, and it sure as heck is not allowed over a town. Take it from my experience, there are lots and lots of total boneheads out there with pilot certificates that pay absolutely no attention to the rules, and are an accident waiting to happen. You just hope that when it happens, they dont take innocent people with them because of their stupidity.