Centro de Periodismo Investigativo (CPI) is an investigative newspaper in Puerto Rico, and with the help of DDB they used twitter right. They created 2000 twitter journalists who all followed 2000 people (that famous twitter limit), and then paid attention. They saw what ordinary people tweeted, famous people tweeted, government employees tweeted and sometimes they find things that lead to stories... This is a nice new twist to the twitter establishment, and it knocks the usual tactic of having a "announcement account" that follows no one off its perch. Nicely done.
CPI - 2000 investigative twitter journalists - (2013) case study (Puerto Rico)