Obama missed a fantastic publicity opportunity. Can you imagine how his political stock would have climbed had he said...
"I am extremely humbled by this. And I cannot possibly express how much I appreciate your confidence in my ideas and efforts. However, given the enormous accomplishments of those who have received this esteemed prize in the past, I feel I must decline it. There is a tremendous amount of work for us, as a global community, to do together. And I hope that when we look back upon our concerted efforts to forge a new path toward long-term global peace and prosperity, we'll do so with the satisfaction of knowing we accomplished it together."
Or, something like that. You know... lots of emotional phrasing that doesn't actually "say" much.
Of course, this assumes he wasn't lobbying for the prize. I'm not that optimistic.