I feel it is a legitimate purpose of the Nobel committee to foster peace-related initiatives, as well as to recognize peace achieved or peace struggles in progress.
Domestic tensions, particularly those surrounding health care reform--and even more specifically the highly partisan and uncivil attacks against the President by right-wing Republicans--in part mask from many Americans the profound positive change President Obama's stated intentions have had on much of the rest of the world and the course of myriad diplomatic initiatives. The President of the United States profoundly--in fact, uniquely--affects the tone and direction for international diplomacy in ways with far-reaching, global implications.
It is completely fitting for the Nobel committee to recognize that the President's actions thus far and his stated intentions for the future, as they relate to nuclear non-proliferation, environmental sustainability, Israeli-Palestinian peace, and multilateral diplomatic engagement in general, deserve urgent endorsement and every wish for success. That is what the peace prize in 2009 does: it stands today for recognition of the President's articulated vision for a more peaceful future in a way that says, "This should not wait. Let us all act now to make this happen, together."
Without the President's efforts--even if they represent leadership by way of goals primarily stated, not met, and processes just begun, not yet vindicated--the world would be one with less hope for a better future, and there would be significantly less momentum along numerous diplomatic fronts toward peace.