Read up on Sabu and the timeline of events between his initial arrest and the various Anonymous Operations. He's a narc, has admitted it and was very much involved in most of the operations. Coincidentally, most people in those operations were rolled on and his assistance has been used in their arrests/cases.
Check the timelines. Some of Lulzsec's most dramatic attacks were carried out with an FBI agent literally looking over Sabu's shoulder.
'Opdarknet' in particular seemed quite a bit different from the rest, in the MO (basically the same as the FBI used against Freedom Hosting) and the wording of their release.