Why does this not surprise me?

Juan Cole:

The Arabic text of the recently released letter alleged to be by Zawahiri (al-Qaeda's number two man) to Abu Musab al-Zarqawi in Iraq raises questions for me as to its authenticity.

[...]

My gut tells me that the letter is a forgery. Most likely it is a black psy-ops operation of the US. But it could also come from Iran, since the mistakes are those a Shiite might make when pretending to be a Sunni. Or it could come from an Iraqi Shiite group attempting to manipulate the United States. Hmmm.

The authenticity of the letter has also been questioned by al-Qaeda in Iraq.

You don't suppose that this has anything to do with the "interception" of such a letter, do you?