Noam Chomsky interview (via randomWalks).

Bin Laden's purpose:

they are fighting a Holy War against the corrupt, repressive, and "un-Islamist" regimes of the region, and their supporters, just as they fought a Holy War against the Russians in the 1980s (and are now doing in Chechnya, Western China, Egypt (in this case since 1981, when they assassinated Sadat), and elsewhere

also:

As for a response, they are, I presume, listening to the foreign leaders, specialists on the Middle East, and I suppose their own intelligence agencies, who are warning them that a massive military response will answer bin Laden's prayers. But there are hawkish elements who want to use the occasion to strike out at their enemies, with extreme violence, no matter how many innocent people suffer, including people here and in Europe who will be victims of the escalating cycle of violence. All again in a very familiar dynamic. There are plenty of bin Ladens on both sides, as usual.