Lily-white couture aficionado Marissa Mayer is a champion of her gender at Google, struggling to ensure that 25 percent of its engineers are women. How is she doing on other measures of diversity? Google has come under fire from Congress for offering H-1B visas to foreign workers rather than increasing its numbers of African-American hires. Perhaps the problem lies in its executives' social circles. A collage of Mayer's Facebook friends in the Google network reveals very few faces that are not white or Asian.