That Obama now shares the same award given to Yasser Arafat should not be surprising--both possess(ed) notable skills in the art of BS'ing people, which is the root of all diplomacy. Neither accomplished enough to earn their awards, although Arafat probably had a thicker resume. But such is liberalism--it's the thought that counts (and apparently pays).
Two questions. One, can he legally or ethically accept this award? Two, if he does will it color his decision-making in any way? Actually another question might be whether the Nobel committee was intentionally trying to affect world events by saddling a US president with a pre-emptive peace award? Obama must reject this thing. He must, right?
Well, the Volokh guys probably know the legal answer because their server is down right now (following this link) but hypothetically speaking if he accepts the award Obama cannot help but think "but I'm the Nobel Prize winner" during every decision. Like whether to put more troops in Afghanistan--or even to authorize a Predator strike in Pakistan of suspected HVTs. Or to bomb Iran. Or in dealing with Israel after they bomb Iran.
But what happens if he does turn it down then proceeds to bomb or render or keep KSM locked up through next year without trial? Does he then become a warmonger overnight? Seems an awful heavy burden.
Yet it might help him on the things he really cares about--health care and global warming. Who wants to argue with a peace prize winner against helping the sick and the poor while saving mother Earth?