Another Occupy Wall Street activist's Twitter account subpoenaed

Just one month ago, the Manhattan District Attorney's office subpoenaed the Twitter account of Occupy Wall Street participant Malcolm Harris, aka @destructuremal. Today, Jeff Rae received word of the same. He has published a copy of a notice he received from Twitter, which was accompanied by a copy of the DA's subpoena. A cover letter from the DA's office indicates that Rae was one of five total accounts subpoenaed. Who are the other four? And why?