"Untitled" by Mark Rothko, on display before auction at Sotheby's, New York, in May. Does its value stem from its pedigree? Or is it valuable because of its contribution to the ongoing dialog that is human expression through the ages? Emmanuel Dunand/AFP/Getty Images hide caption

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President Barack Obama speaks at Nelson Mandela's memorial service in Johannesburg. Standing to his right, Thamsanqa Jantjie gestures as if he is interpreting the speech for the deaf community. Alexander Joe/AFP/Getty Images hide caption

itoggle caption Alexander Joe/AFP/Getty Images