Chris Kresser posted a new article today about B12 that has already produced an astonishing number of comments. The article discusses new, more sensitive testing, deficiency stages, and rates of B12 deficiency amongst vegetarians and vegans.
http://chriskresser.com/what-everyone-especially-vegetarians-should-know-about-b12-deficiency
http://chriskresser.com/what-everyone-especially-vegetarians-should-know-about-b12-deficiency