Almost a decade in the industry and I have never worked with another black developer. One time I was on a team with a black project manager who use to be a developer but that's it. For all the pushback on diversity recruiting I appreciate events like Google sandbox that remind me that we do exist and present opportunities to network.
Working in technology in the public sector, where women and racial/ethnic minorities underrepresented in technology as a whole are generally less underepresented than is generally the case, I've worked with...two others, in a similar time frame.
Some companies are genuinely concerned. When I left a major corp, the VP of Software Development called me into his office and said (paraphrasing) "since you're leaving I can count on you to be honest with me. Are our diversity programs doing anything useful or are we just kidding ourselves?"
The company I went to after that (another large corporation) hired a consultant to interview a set of women and minorities to try to understand how comfortable they felt in their day-to-day roles. Again, knowing the HR people there, I felt they were genuinely trying to foster a pleasant environment, but that's also the company where I came across that one black developer.
Then again, I do recall travelling across the country to be my company's Expert for a deposition for a lawsuit over a project I was on and having the opposing party think I was the cab driver...