“To try it, just go to a friend’s posted item in your news feed, click “share” and you’ll see a “via [your friend’s name]” (with an option to remove it). Once shared, the item will appear on your profile, with a via link that points to your friend’s profile. Your friends will also see the item in their News Feeds, creating the viral loop that is the Twitter (Twitter) retweet.”
The feature is only active for posted links and not other items such as status updates or photos. Also, you’ll only see the *share* link on newsfeed items that are posted for public view (i.e. based on the privacy settings set by the Facebook friend who you are quoting).
The new feature is now live for all Facebook users.