I must admit I dislike the BMI (Body Mass Index), which is a ratio of your weight vs your height (http://en.wikipedia.org/wiki/Body_mass_index). It does not take into consideration how muscular you are or how in shape you are or you strength or what your body fat % is. A truly buff person (not me) will come out as obese. While I don't like the sites that talk about it as they're out to prove the obesity epidemic is a myth and I don't believe that - it is a problem. But this site (http://www.obesitymyths.com/myth1.1.htm) among others lists several famous people who are technically overweight if you use BMI alone.
Now in all fairness, the BMI has me tagged correctly. I am slightly overweight. However as I get more and more in shape the BMI is not going to reflect that and in fact it may show it as getting worse as I'm gaining muscle and that's heavier than fat.
One site (http://www.nhlbisupport.com/bmi/) even says that the BMI is a calculation of your body fat %. Is that right? How could that be? Though the BMI computed for me now is not too far off the mark, when I gain muscle, my body fat % goes down (according to my Tanita scale), but my BMI goes up.
Now in all fairness, NIH does have a page talking about the limitations of the BMI here: