I think that the Peace Prize was given to Obama for who he is, what he represents and what he’s done.
Let see..
Who he is – first US black president.
What he represents – demonstrates that a black person in the US could become president (even with some radical ideology behind him)
What he has done – really nothing (voted present most of the time while in the senate), he was nominated just a few weeks into his term. He has continued many of the policies that Bush left behind, that the Democrats were assailing, but those same policies are supported by the Democrats now Obama is in office.
This breaks down to being nominated for the first US black president and that he demonstrates that a black person in the US could become president. Its not a bad thing, but really not worthy of a Noble peace prize.