It's never quite clear what the Nobel Peace Prize means. Remember that Arafat got one? When I lived in Sweden, my friends there explained it by pointing to the awarders: "They're Norwegians, don't forget!"
Unlike the science prizes, the Norrmen use their prize as a way to influence events, not just recognize past achievement. I'm sure this is part of what the Norrmen tried to do here, that and as others have said, to compliment America in finding someone who is not George Bush.
But more profoundly, this year I think the Norrmen have made another error - they have forgotten that they are the MVP committee, and instead found the Rookie of the Year.