As you know I am not a fan of Obama but his award was a salute to being the first black president of the US and had nothing to do with his peace efforts...I am not sure that was actually what the Peace Prize demands, the criteria is have effected an action that contributed to world peace. Specifically it aims to promote efforts at arms reduction, dialogue between nations and the resolution of specific conflicts.
So TR for the Treaty of Portsmouth resolving the Russo-Japanese War, Gorbachev for reducing the world stockpile of nuclear weapons and yes even Yassir Arafat for the Camp David Agreement. I would agree that Obama did little to earn his peace prize under the criteria of the award but subsequent military actions nor prior do not invalidate awards. Nobel it should be remembered made the money for the prize from the production of explosives and military firearms propellants. He realised that to encourage peace he would need to deal with men (and later women) who had to deal with a real and all too often violent world. The path to peace being incremental steps not impossible standards.