Are you referring to the Twitter section? It changes the URL automatically upon submission.
For example, when I click the twitter button in this link
http://www.politicalgroove.com/news/...es-u-turn.html the it grabs the post title and the URL and looks like this (in the box before you submit):
north korean ship does a u-turn - PoliticalGroove Forums
http://www.politicalgroove.com/news/...es-u-turn.html
Then after you submit, it automatically changes the URL to shorten it, like this:
http://bit.ly/OH0tU