Yes, I hear that, but I do not believe it. Deaths of key figures almost always have serious negative reprecussions for the side that experienced the loss.

Yamamoto's assassination removed the best brain in Japan's high command and thereby hampered Japanese strategic organization, hastening the downfall of Japan.

Che Guevera's assassination began the dissolution of his terrorist organization in South America.

When Attila the Hun died, the Huns ceased conquest and began a gradual assimilation with the conquered peoples.

When Alexander the Macedonian died, the Macedonian Empire ceased expansion and broke up into separate states.

And so on, throughout history, loss of leadership has proven disastrous for the side that suffered the loss.

Zarqawi's assassination definitely will hurt Al Qaeda.