More on the question of whether it is a fake/forgery. My article Zawahiri 'Letter' Draws Increasing Skepticism is now up. Some points on this issue derived from Jean-Charles Brisard's recent book on Zarqawi.
-on the crisis of media Zawahiri mentions: JCB notes that Zarqawi counted on his semi-public executions evoking terror b/c of their barbarity. "He is a master of the art of communication who has even established a 'media department' within Tawhid wal Jihad..." That dept. is said to have 3 staff members in Iraq and computer facilities based in other countries, and utilizes modern tech, combining audio and visual effects in a way that reinforces the impact of the execution. (Not the picture of a Zarqawi who has not thought about media impact, as portrayed by the letter.)
-Zarqawi's group commits fewer terrorist acts than other groups in Iraq. (per JCB)
-While some religious Iraqis condemned the acts outright -Zarq. has always justified them.
-al Qaeda's commitment to the 'cause' in Iraq developed after religious radicals "authorized" Zarq's group's activities, including the executions.
-There was "a markedly large growth in the number of applicants for jihad since the summer of 2003..."
-Zarqawi's execution of Nicholas Berg led to a wave of hostage-takings.
-Consider also JCB's point that in the August-September issue of Voice of Jihad (an al Qaeda organ) Abd El-Rahman ibn Salem Al-Shamari was "full of praise for the beheading of an Egyptian in Iraq." Zarqawi was referred to positively, as the "sheikh of killers." He was urged to "Be merciless!"
On whether Zarqawi is in Fallujah; for consideration -JCB notes at the time of the American assault in November 2004, Zarqawi had already fled Iraq weeks earlier and was calling for jihad in press releases and exhorting the "courageous resisters of Fallouja."
Of course informaton on establishing the caliphate and using Iraq as a training ground and base of operations to send jihadists out for missions elsewhere has ample documentation elsewhere.
Perhaps more information will be forthcoming on the Zawahiri letter.
Of couse, as I've previously noted, obeserved anomalies are just that -questions waiting to be answered. But they do seem to be piling up.