For the reasons Drew has already posted but also, speaking realistically, Obama hasn't put her away yet.  She is still within striking distance.  One major gaffe by Obama and she's in.  

One analysis posted on MyDD put it thus:  if things go according to predictions Obama will need ~35% of the PLEO delegates at the convention to win the nomination while Clinton will need ~72%.  That would be hard for her to accomplish both from a "What's In It for Me" stance as well as the demonstrated incompetence of the Clinton campaign.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre