Delegates NOT voting for Obama??

Many facets of our political process can be confusing, including what exactly the responsibilities of the delegates to a political party convention are.

I listened to two Democratic party delegates interviewed on NPR this morning and they were each asked if they would, in fact, be casting their vote for Barack Obama. One said she would not - instead, she would cast her vote for Hillary Clinton because those were the intentions of the people who chose her as a delegate.

I find this odd because, as I understand it, at this evening's Democratic Convention Hillary Clinton will be formally releasing "her" delegates of their duties to cast their vote for her (even though she didn't win her party's nomination her name will appear on the list as a formality, which is basically what the purpose of the convention is - a formality) and choose Obama as the Democratic nominee for President of the United States.

I understand delegates wanting to honor the wishes of those who chose them to be a delegate, but if the nominee (Hillary) releases them of that obligation, why would they splinter the party and vote for someone who isn't the intended nominee? It seems stupid - like banging your head into a wall.

Did I confuse you? Good. Welcome to American politics.