The Telegraph has it right:

What this does is accelerate the elevation of President Obama to a comedy confection, which he does not deserve, and gives his critics yet another bat to whack him with. Shame on the Norwegians. He should turn it down, even if he does look great in white tie and tails.

Seriously, if he had an iota of humility (which I'm not sure he does), he would turn it down. It would be the first really brave thing he's done (as opposed to said) in quite a while. And frankly, the credit he would earn from turning it down would be far, far greater than from accepting it.