The Department of Justice has subpoenaed many people's Twitter accounts who were associated with WikiLeaks. The subpoena states that there is "reasonable ground to believe that the records or other information sought are relevant and material to an ongoing criminal investigation."
The users who were subpoenaed are Birgitta Jónsdóttir (a member of the Parliament in Iceland), Jacob Appelbaum, Rop Gonggrijp, and, of course, Julian Assange. According to Salon:
The information demanded by the DOJ is sweeping in scope. It includes all mailing addresses and billing information known for the user, all connection records and session times, all IP addresses used to access Twitter, all known email accounts, as well as the "means and source of payment," including banking records and credit cards. It seeks all of that information for the period beginning November 1, 2009, through the present.
No one is currently sure what the subpoenas entirely mean, but no matter what the reason, it's a serious effort from the United States DOJ to somehow obtain information and/or intimidate any person(s) related or associated with Wikileaks. It's kinda more than a little bit scary. [Salon]