Posted 9/17/2011 8:31 AM (GMT -5)
The short answer is that it won't hurt you if you have no problems with drinking milk because that's what it is. More of the friendly bacteria multiplies the longer the yogurt sits unrefrigerated.
Long answer: And as the yogurts sits (before refrigeration) more of the lactose is consumed by the good bacteria. People who have difficulty digesting lactose have an easier time digesting yogurt that is aged, meaning less lactose is left and more good bacteria is there. But this only happens when the yogurt is allowed to sit in a warm place (not the refrigerator) for 12-24 hours before refrigerating (where it firms up).
To eliminate even more lactose you can make "Greek" yogurt which is thicker, more like sour cream, by using cheesecloth or something similar to drain the whey from the yogurt. Really delicious.