Everyone is skimming what I said. Law is they must be at least 1000 feet.
Actually, no. The rule is 500 feet from any person, vessel, vehicle, or structure except as required for takeoff and landing. In congested areas, MSA is 1000 feet above the highest obstacle within a horizontal radius of 2000 feet.
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div5&view=text&node=14:2.0.1.3.10&idno=14#14:2.0.1.3.10.2.4.10
So, an airplane at an altitude of 400' above ground level displaced horizontally 300' from you would be flying IAW the rule. 500' is actually pretty close (less than two football fields). However, if an airplane can fly at 50' AGL and maintain the 500' separation from any person, vessel, vehicle, or structure, that pretty much defines a "sparsely populated" area (at least as the FARs apply).
Having said that, polluting OPP with noise from operations strictly IAW the rule is still violating the good neighbor policy that one would expect.