Osama Obama IS NOT the President elect yet, and may never be. We will see what the Electors decide mid-December about supporting an illegal alien as President of the US. McCain may yet win.
It is conventional to refer to a candidate who has won states with enough electoral votes to win in the electoral college the 'President Elect' even before the electors vote. The most likely reason for him never to be president elect would be invaders from outer space taking over. There are also some more unlikely scenarios.