I've just finished watching "Who Do You Think You Are?" where Blair Underwood was researching his ancestry. While trying not to be too critical of the genealogists who were doing his research, who were white, I do think that he might have been better served to have had at least some input from a black genealogists because the research that was done for him seems to have been through the eyes of people who jumped to a lot of conclusions, and just stopped. For his ancestors who were concluded to have been slaves and couldn't be found in the census prior to 1870, there was no mention of the fact or at least no attempt to try to determine who the slaveowners may have been, in which case it may have been possible to find earlier records of his ancestors through the slaveowners.
But most telling was the findings that he had free ancestors who were SCOTTs and HUMBLES and that they had been free at least before 1806. If the persons who researched for him had bothered to check out Paul Heinegg's work, they would have found that the SCOTTs were free people of color for an awfully long time. And more importantly, the HUMBLES family were free at least from the 1740's, and in fact, that the "Tabby HUMBLE" of Amherst Co., VA, that was Underwood's ancestor, was even mentioned specifically in Paul's work as "Taba HUMBLES" and was very likely to have been the daughter of Martha HUMBLES, a free woman of color who lived in Amherst Co.
I don't expect the show to be perfect, but it certainly would help if they would provide more thorough research methods for the black celebrities they are researching by having some input from black genealogists who would know that there is more to it than just stopping at that 1870 brickwall and who know about more resources than what is being shown.