There are a number of possibilities here.
Born in US to two citizen parents. NBC by any criteria.
Born in US to one citizen and one non-citizen parent. (BO's situation.)
Born outside the US to two citizen parents.
Born outside the US to one citizen and one non-citizen parent. Some believe father or mother being citizen should make a difference.
Personally, I define NBC as "citizen at birth."
But would take SCOTUS ruling to settle it.
Sorry, forgot born in US to two non-citizen parents. Also known as the anchor baby.
So, Putin, Chavez, Castro could pop a kid here, and the kid is a NBC?
Nuts, that is not what the Founders or the 14th intended.