Steven Spielberg has withdrawn from his role as artistic adviser to the Beijing Olympics to protest China's policy towards Darfur. Seemingly, yet another example of "celebrity activism" around human security issues. I blogged about this before. As I continue to think about the role of celebrity activism in human security campaigns, I've been pondering who actually counts as a celebrity? Performers clearly do. But what about other well-known members of the entertainment industry - writers, producers? What about well-known figures who perform public, rather than media roles? In a digital...