This is awkward. It appears that HP's new webcams, which have facial-tracking software, can't recognize black faces, as evidenced in the above video. HP has responded:
We are working with our partners to learn more. The technology we use is built on standard algorithms that measure the difference in intensity of contrast between the eyes and the upper cheek and nose. We believe that the camera might have difficulty "seeing" contrast in conditions where there is insufficient foreground lighting.
[HP and Metafilter via The Daily What]