On April 26, accused Wikileaks source Bradley Manning's friend and supporter David House tweeted "Subpoenas are being issued in the WikiLeaks grand jury. Violations of Espionage Act. No further comment at this time." House is one of the few people who has visited Manning in detention in Quantico; where the former Army intelligence officer has been held for months before a recent transfer to Leavenworth, Kansas.
House later added that he did not receive a subpoena himself. The identity of the recipient is not yet publicly known.
From the Wikileaks Twitter account that same day: "Fresh subpoenas are being issued in the WikiLeaks Alexandra, VA secret grand jury in relation to the espionage act."
Glenn Greenwald at Salon writes that the FBI served at least one subpoena in Boston, and that this was presumably related to the Wikileaks case.
Notably, the Subpoena explicitly indicates that the Grand Jury is investigating possible violations of the Espionage Act (18 U.S.C. 793), a draconian 1917 law under which no non-government-employee has ever been convicted for disclosing classified information.
And Wikileaks, being Wikileaks, tweeted out the D.A.'s phone number.