My uncle does triathlons and used to be an Olympic-grade rower. He counts as "morbidly obese" on the BMI scale. In the majority of cases, I'd say that BMI is useless.
And on the thread subject - yesterday I had to tell a 27 year old man the difference between an "abbreviation" and an "acronym". *facepalm*
If a person has a greater-than-average lean body mass, BMI is going to be inaccurate, because it's calculated based on the assumption that a person has an average amount of muscle. For a majority of average people, it's a meaningful number, but for athletes or anyone who has more muscle than the average person of their height, it's going to be inaccurate.
LBM is a very important number in calculating the 'correct' weight for an individual. I once had mine done, and discovered that while I was overweight, my LBM was at the exact point where I always leveled off on a diet. My LBM was about 35 pounds higher than the BMI scale said my correct weight should be! No wonder I'd start to plateau at that weight; I'd lost most of the excess fat, and was now trying to lose muscle. I was pretty active at the time, using a bike as my primary means of transportation, and also doing weight lifting. No one, including my doctor, could guess my weight within 20 pounds. Even though I had excess padding, I was still built like a brick house.