Liu Injured?

This is not official news, but within an article about Bolt’s 9.72.

"Leading into the 100, the crowd watched as Chinese hurdler Liu Xiang announced that he would not be racing due to a tightened right hamstring, and his coaches said it is unlikely that the 2004 Olympics 110-meter hurdle champion would race again before the Games.

Leaving his coaches and handlers to speak for him, Xiang hopped – he did not hurdle – over a side fence, nimbly so, with two feet and both hands on the fence top."

It is a long time between now and the Olympic Games for him not to be racing.