Summary of Rules and Requirements, Google Lunar X Prize
"The competition's grand prize is worth $20 million. To provide an extra incentive for teams to work quickly, the grand prize value will change to $15 million whenever a government-funded mission successfully explores the lunar surface, currently projected to occur in 2013."
China's Chang'e-3 to land on moon next year, China Daily
"Ma said the Chang'e-3 would probe and explore the lunar surface, and carry out various environmental and space technology related tests. It will spend 15 days on the moon to lay the foundations of what he called, further deep space exploration."
Chang'e 3, Wikipedia
Keith's note: None of the Google Lunar X Prize competitors will be capable of landing on the Moon during 2013, so it is a foregone conclusion that the prize will drop in value. Add in the lack of real (existing) flight hardware, firm and fully-funded launch contracts, and all other funding required to cover other mission aspects of launch and operations, and it is becoming increasingly unlikely that any of the teams will be able to meet the Prize's requirements by 31 December 2015. I would most certainly like to be proven wrong when someone lands on the Moon.