If Obama was born in the U.S., but his mother had failed to live in the U.S. for five years after the age of 16, then he is not a natural-born citizen, because his father was not a citizen. Thus, even if Obama proves he was born in the U.S., he has not proved he was a citizen.
In fact, it seems now proven that Obama is not a natural-born citizen, because:
His father was not a citizen; his mother was not 21 years old; thus, she had failed to live in the U.S. for five years following her 16th birthday.
Can you imagine the media circus if this ever became a court case? It would make Bush v Gore look like Sesame Street.
I wonder if this is what the passport information breech was about a few weeks ago?
If Obama was born in the U.S. then he's a U.S. citzen per the 14th Amendment regadless of his father.