Nielsen is reporting that seven shows placed among the top ten primetime programs among both African-American and white viewers during the 2006-7 season. In contrast, ten years ago during the 1996-7 season there was only one show in common (Monday Night Football).
I'm a numbers geek from way back, and I remember reading the lists of the most popular shows among the different ethnic groups long ago and it did surprise me that they were so different.
I'm not at all sure what I'd attribute the convergence in interest today, particularly when the number of available shows today is so much greater than it was 10 years ago.
One easy answer is that two shows strike a chord across the country, American Idol and Dancing with the Stars. 5 of the 7 shows on the top 10 list crossover were episodes of those two shows.