The devision was to be expected. You can't get a group of people who all want the same thing together and give them two choices. I think this a great example of what can happen when you bring passion into politics. If we as voters went along with apathy we are known for, none of this would have happened.
I don't think we can blame Obama or Hilary or their supporters for this. There is a division but its only because people are too set in their opinions of one versus the other. What is wrong is the entire mentality of "well, Hilary didn't win so I am voting for McCain". People just need to get over themselves.