Wall Street traders mine tweets for investing clues

``Online surveillance of social-networking sites is emerging as a must-have tool for hedge funds, big banks, high-frequency traders and black-box investment firms that run money via computer programs. The goal: to gather market intelligence from previously untapped sources... The conversation tying tweets and social media and stocks together has gotten louder ever since last September, when an academic study at Indiana University in Bloomington found a correlation between the collective mood of millions of people identified by tweets and the direction of the Dow Jones industrial average.''