FYI, in comments over at chez Clemons, Steve says in response to my speculation:
I don't think that Holbrooke or Gelb would do it, as it might seriously undermine their former staffer and structural link to the UN, Bob Orr. I don't know who would leak this, and it may be dangerous to speculate. I know Kathy Bushkin pretty well -- and she is very tight-lipped. That leaves Tim Wirth or John Ruggie, or the one I don't know -- Nader Mousavizadeh.
Tim Wirth would not leak such a meeting -- he's more careful than that, and if it happened, it had to be accidental. But the material that Warren Hoge got was quite detailed -- so accidental disclosure seems unlikely. That leaves Ruggie and Nader Mousavizadeh.
I can't comment on Nader. Ruggie could have done it because of frustration with the slow progress of Annan's reform -- and since he's no longer on staff at the UN, he might have fewer stakes in keeping this quiet. His name gets in the news a bit. He's one of the lesser known personalities in the group and might benefit from exposure.
Gelb, on the other hand, is not the most careful guy in the world -- and has been in the news an awful lot lately because of his quick out of the box assault on Bush's early inaction on the tsunami/earthquake crisis. Gelb might have gotten carried away in his commentary and given Hoge material on this and other matters Gelb is involved with.
Who knows...this is all speculation. But I do think that whoever did leak this news hurt Holbrooke and Orr.
That said, I think that the advice that the group gave to Annan was pretty good.