I believe many people (including Obama himself) were surprised by his winning the prize. I don't think race was the primary reason (official or otherwise) behind his being awarded the prize. Among the main reasons for his nomination were "Obama's promotion of nuclear nonproliferation and a 'new climate' in international relations fostered by Obama" [1]. One pessimistic view of this statement is that Obama was essentially awarded this prize for not being Bush, who was perceived by many in the international community as damaging the state of dialog between nations. Arguably, this could promote peace. The view was not without criticisms :)

[1]http://en.wikipedia.org/wiki/2009_Nobel_Peace_Prize