At Chirp developer conference, "we mentioned if you want to share a link through Twitter, there currently isn't a way to automatically shorten it and we want to fix this. It should be easy for people to share shortened links from the Tweet box on Twitter.com. To meet both of these goals, we're taking small steps to expand the link service currently available in Direct Messages to links shared through all Tweets. We're testing this link service now with a few Twitter employee accounts.
When this rolls out to users, all links shared on Twitter.com or 3rd-party apps will be wrapped with a t.co URL. A long link; http://www.amazon.com/Delivering-Happiness-Profits-Passion-Purpose/dp/0446563048, wraps as http://t.co/DRo0trj for display on SMS, but it could be displayed to web or app users as amazon.com/Delivering- or as the whole URL or page title," writes Twitter.