As I am apparently the sole defender of President Obama's Peace Prize on the internet, I feel inclined to point you to the interview with a member of the Prize Committee:
http://nobelprize.org/mediaplayer/index.php?id=1174He may have only been in office for less than a year, but:
1) The prize is INTENDED to reward things done within the year
2) He has been campaigning under similar principals for much longer
3) What Obama has "done" is not as concrete as a treaty, but does indeed closely follow Nobel's will in that his actions and plans have done much to promote an international community
4) The Nobel Prize Committee says itself that part of their choice is in giving Obama a public token of support in the hopes that it will aid him in
continuing along the path upon which he has set
EDIT: The President gets it! Quote: "I do not view it as a recognition of my own accomplishments. But rather as an affirmation of American leadership. ... I will accept this award as a call to action."