I did. An American survey in 1996 found acceptable levels were being consumed. 12year old results. Think 12 years ago some people on these forums were probably still on Formula.
Studies found some tests infact were inadequate to diagnose low levels of B12 as per
http://www.news-medical.net/?id=5908 ( circa 2004 so far more recent than your proposed studies ) Not necessarily affecting the 1996 survey but just another thing to digest. Also the BMI for the average american teen has ballooned since that time so I wouldn't bet on the numbers being accurate
An overdose of B12 can be unhealthy but that is taking about 1000% more than the daily recommended allowance.