Washington rumors now have Hillary Clinton being considered as a possible selection for Secretary of State by Barack Obama. Hard to imagine Obama making this choice. His relationship with the Clinton camp is cool at best, and would effectively shut down any hope Clinton had for her own presidential run in the future. If he won reelection in 2012, she would not have a clear path to the nomination until 2016, when she will be 69 years old. Playing third fiddle to Obama wouldn't do much for her image of leadership either.
Considering that the SOS is the voice of the President to the world, it would be an extremely risky choice for Obama in a position where total personal loyalty is critical.