I posted something a few days ago about the apparent futility of leadership decapitation as a strategy against al-Qaeda, or most other kinds of terrorist groups. AQ has experienced a brisk turnover in its middle management ranks - thanks to Predator drones - but those losses have had little evident effect on its organizational coherence.
Along those lines, here's a report from Jane's Strategic Advisory Services about al-Qaeda and the adaptability of its command and control structure.