What % Makes One Black ?

Some discount Tiger Woods', Halle Berry's or Barack Obama's level of Blackness - Why?
Is half-Black not really Black?
What about Obama's daughters? Is 3/4 Black, Black enough?

Marcus commented that he would disown his progeny if they brought home a partner who wasn't Black.
A lot of families do the same.
A large part of me growing up with my (almost useless) mother and my mean-as-hell step-father was that it was in defiance to my grandmother. (That, and I had two younger half-brothers that I wished to protect from their circumstances.)

My paternal grandmother (well.. both grandparents) could have offered a much more comfortable life.
At least once a year, I would take a break from my tumultuous home life to be spoiled by my grandparents.
During every summer or Christmas break spent in Texas, they would offer some type of incentive (money, motorcycles, cars, trips abroad, etc) for me to be raised in a "better" environment.
But my grandmother hated my mother - and even though I didn't see the value of having her, she was still my mother.

My grandmother hated her half Mexican/half Native American daughter-in-law but loved her grandchildren with half of the same genetic make up?
I couldn't see it.
In fact, the only reason the entirety of their inheritance went to me was because I was the only grandchild who refused to be bought.
They respected (but hated) my insolence.

But what makes me Black?
Is it the experiences acquired while living in the hood? (Is living in the hood requisite?)
Is it the color of my skin? (What "color" is Black?)
If I was brought up by my somewhat well-to-do Black grandparents - would I be more Black or less? (If one has more opportunity - are they less Black?)
Is it the whole of my family's culture? (Which one?)