I have to agree that they have created a martyr rather than killing the organisation. Oh it is a brilliant PR move, full of 'feel-good' decisive action and a 'sense of closure', but it is not a solution to the radical branches of Islam that are cropping up. (on a related note, judging Islam by the actions of Al Qaeda is like judging Christianity by the Westboro Baptist Church)
The terrorism is a symptom of a large problem, but the cause is left un-addressed.
Consider the possibility that 9/11 was an isolated event. A small group of nutters managed to pull off a big token gesture and a few people who hated the US gave them a metaphorical pat on the back.
Next thing you know, we have a lot of idiots attacking Islam (both verbally and physically) because the attackers were Muslims. I saw police vans outside mosques for the first few weeks after the attacks (and again after 7/7) just to protect them. I have known loads of Muslims who were thoroughly nice people, but none who ever expressed extremist beliefs. The Muslims, unsurprisingly, will start to feel just a little resentful. They are being picked on by racists who call them terrorists, which is never nice.
One symptom of this resentment is the rise in the number of fundamentalists. Still not terrorists, we are just talking about people going to the temple more often, maybe wearing the headscarf. Of course, the rise in attendance means that the mosques get overcrowded and so they want to build new ones. The racist idiots see the increased number of headscarves and applications for planning permission to convert a building to a mosque, then scream that it is an invasion.
Public opinion (or at least that fed to them by the Daily Mail and the Sun) leads to pressure on local government to deny planning permission to mosques and to ban the headscarf on (usually, but not universally) pretty flimsy ground. For some reason, Muslims start to get upset that they are not allowed to dress as they want or build mosques that they are willing to pay for out of their own pocket.
How surprised can anyone be that some Muslims feel like they are under attack?
The majority might just feel put upon and do nothing, but how surprised should we be to learn that some (a smaller number) believe that they need to fight back?
Even if the majority of these opt for political pressure and public debate, should we be surprised that a tiny number turn to terrorism?