Jamaica's Usain Bolt wins his third gold medal after the final for the men's 4x100-meter relay at Beijing. (AP Photo/David J. Phillip)

United States' Michael Phelps celebrates after winning his eighth gold medal after the men's 4x100-meter medley relay final during the swimming competitions at the Beijing 2008 Olympics. (AP Photo/David J. Phillip)

Stephanie Rice of Australia, a gold winner at the 2008 Beijing Olympics, looks to be one of other top gold medalists to add to their collection this summer in London. (AP Photo/Itsuo Inouye)

Natalie Coughlin of the United States, right, celebrates after winning the gold medal in the women's 100-meter backstroke final at the Beijing Olympics. (AP Photo/Thomas Kienzle)

Cuba's Dayron Robles crosses the finish line to win the gold in the men's 110-meter hurdles in Beijing. (AP Photo/David J. Phillip)

Ethiopia's Kenenisa Bekele takes gold in the men's 10,000-meter final during the athletics event at 2008 Olympics in Beijing. (AP Photo/David J. Phillip)

Spain's Rafael Nadal reacts after winning singles match and gold at Beijing 2008 Olympics. (AP Photo/Elise Amendola)

China's Lin Dan in action to win the gold against Malaysia's Lee Chong Wei in the men's singles badminton finals at the Beijing Olympics. (AP Photo/Bullit Marquez)

China's gymnast Chen Yibing performs on the rings during the apparatus finals at the Beijing Olympics, where he won the gold medal. (AP Photo/Rob Carr)

Russia's Yelena Isinbayeva breaks the world record as she wins gold in the women's pole vault final at Beijing Games. (AP Photo/Julie Jacobson)

USA's gold medal winner Mariel Zagunis, center, on the podium after the women's individual saber event at the Beijing 2008 Olympics. (AP Photo/Andrew Medichini)

Britain's Chris Hoy shows his three gold medals for track cycling at the Beijing 2008 Olympics. (AP Photo/Christophe Ena)