The Norwegian Nobel Committee said it gave the prize to Obama for his "efforts to strengthen international diplomacy," his "vision of and work for a world without nuclear weapons" and for inspiring hope and creating "a new climate in international politics."
Emphasizing diplomacy ahead of force is a big improvement, but at this point it's mostly just rhetoric. He's only just started to accomplish something in Iran with diplomacy. Elsewhere, we're still fighting TWO wars and he's considering escalating one of them. He's effectively covered up and excused much of the previous administrations' torture and gross human rights violations and Guantanamo Bay remains open and running. He increased the size of the "defense" budget. He has spoken about ridding the world of nuclear weapons but not indicated how that could happen nor done anything about it. He has made no appreciable progress in Israel and Palestine.
Obama does not deserve this award. I hope that knowing he doesn't deserve it makes him feel obligated to earn it retroactively.