One reason Sen. Jay Rockefeller's staff -- and the Democratic Intelligence Committee staff -- should be target-rich environments for Senate investigators in the Washington Post leak scandal is that they are well-known leakers of highly classified information to reporters.
Earlier this summer -- and there are others on this site who can better detail the story than we can -- it was reported that the Justice Department had launched a criminal investigation into whether Senators Rockefeller, Dick Durbin, and Ron Wyden or their staff had leaked details about a secret "black ops" CIA satellite program in 2004. Details about new spy satellite technology were revealed to the press, and it was determined by the CIA that the programs had been compromised. It is believed that that investigation remains ongoing.
Making the call to investigate your own institution isn't an easy one, particularly because the MSM will spin this as Republicans simply hitting back at Democrats. Senator Frist and Speaker Hastert deserve credit for making the tough call.