Seth writes:
I did an approximation a while back on the bacterial numbers in yogurt (and then was verified on this list by another member, and also by Lyo-San).
See: http://www.healingcrow.com/ferfun/conspiracy/conspiracy.html
"Homemade yogurt that is fermented for 24 hours, as recommended in the book Breaking the Vicious Cycle, will have an average concentration of 3 billion cfu/mL of yogurt".