Interesting thoughts on the issue. In a somewhat related thought, I began to wonder why I've rarely ever seen a black surfer. Being in So Cal, I've spent a lot of time at the beach.
A quick Google search led me to the Black Surfing Association (BSA)
http://www.blacksurfingassociation.com/. Here is a paraphrased quote, "From the need for companionship, commorodary [sic], and socialization on a path shared by so few of our own..." Further into the site it mentions little black representation in hockey, golf, and a few other sports.
It seems to me that in order to get more folks into anything. There must first be a will and an interest. But placing mandatory percentages on graduating classes? My department did it in order to promote more women to the rank of sergeant or any other "coveted" positions. The only way to get the numbers you need (and currently don't have) is to lower the standards. Even then we can't always get the number and have to go to a special board for a waiver.