The root of this problem is simply that there are a lack of blacks with technical backgrounds (of the high-level blacks listed in your post none of them had cs, engineering, or math degrees). If more blacks opt for technical training, the number of blacks in the startup community will grow. For those who do have an appropriate background, funding probably proves to be another barrier. All too many times, I hear of founders raising initial funding of tens of thousands of dollars from "friends and family." For obvious reasons, this is not an option for the majority of black founders.
btw ... Russell Simmons is a co-founder of Yelp
Wow, I guess race is too complicated, even for Hackers. I read your post yesterday and I have since been thinking of how I could post a comment that would express what I think, being a member of a "minority" from Harlem, without sounding like I'm paranoid, or complaining. Something intelligent and not too emotional. I'm still thinking, but I figured I would post SOMETHING. I was kind of surprised/disappointed that there weren't more comments. Then again, maybe the lack of comments says enough.
Race is a complex topic. I wonder how many people will be willing to discuss it here.