my girlfriend is a dietitian.....i'll ask her for her take on it.....but i KNOW its quite innacurate, as it doesn't apply to every body type...
for instance, i saw a chart in her moms office (also a registered dietitian), and it said the ideal weight for someone my size (6'4") was like 160lbs...which is ridiculous! i would be nothing but skin on bones if that were the case and would be quite susceptable to injury.
i weight 225lbs right now, and most people cant believe it as i still look skinny...
so i know skin fold tests and BMI are highly innacurate as they dont account for muscle mass (which weighs more than fat)......something more accurate is called a "Bod Pod". it looks like a little egg that you crawl into, and they pump in pressurized air to measure the air displacement. this test is HIGHLY accurate and is used by the athletic department at our university for their athletes.