suggestions on node form to avoid duplicate nodes

For large organisations with lots of content there's a risk different content creators may create duplicate content unknowingly.

One of the cool features seen when asking a question on stackoverflow is the "Questions that may already have your answer" block that appears below the question title after you've typed it in:

I was wondering if a Drupal contrib module existed for something like this already? There's a bunch of modules listed on this groups page that talk about showing related content, but they're all for front end UX enhancement stuff.