The same one that took out Abu Laith al-Libi, allegedly. His name came up as a possible target after the news first broke, earning this non-denial denial:

[O]ne senior official told ABCNews.com the strike was aimed at one particular figure.

“We don’t know whether we got him yet, we are sorting through it,” the official said, indicating the intended target was a top leader of the terror group.

The official also ruled out as a target American al Qaeda Adam Gadahn, who appeared recently in a propaganda videotape.

“Gadahn may be recognizable to all of you, but he is really not that high up on the food chain in al Qaeda and not that important,” the official said.

None of that contradicts what Rusty’s hearing about Gadahn possibly having been with al-Libi by coincidence and the U.S. getting a lucky twofer in the process. Why would they be hanging around together, though? Al-Libi was a jihadi commander in Afghanistan; Gadahn is, to all appearances, a mouthpiece and media asset. The paper Rusty quotes says they were at a meeting to plan a spring offensive across the border but unless experts have badly underestimated Gadahn’s role in the group he probably wouldn’t be involved in something like that.

Unlike the man himself, seems pretty thin.