http://en.wikipedia.org/wiki/Grigori_Perelman

Section: The Fields Medal and Millennium Prize

Sir John Ball, president of the International Mathematical Union, approached
Perelman in Saint Petersburg in June 2006 to persuade him to accept the
prize. After 10 hours of persuasion over two days, Ball gave up. Two weeks
later, Perelman summed up the conversation as follows: "He proposed to me
three alternatives: accept and come; accept and don't come, and we will
send you the medal later; third, I don't accept the prize. From the very
beginning, I told him I have chosen the third one… [the prize] was completely
irrelevant for me. Everybody understood that if the proof is correct, then no
other recognition is needed." "'I'm not interested in money or fame,' he is
quoted to have said at the time. 'I don't want to be on display like an animal
in a zoo. I'm not a hero of mathematics. I'm not even that successful; that is
why I don't want to have everybody looking at me.'