I certainly believe there are links between poverty and terrorism, but particularly in terms of the West's so-called Global War on Terror, I believe more important are other variables such as the ones mentioned in the prompt, e.g. perceived humiliation, grievances w/ U.S. foreign policy, radical ideology etc.
For instance, certain of the key 9/11 hijackers were reasonably middle (or lower-middle class) young adults residing in European cities. And while others on this E-mail chain far more knowledgeable than me might correct me, the 15 or so Saudi hijackers (of the 19 total) I don't recall having had hugely impoverished backgrounds, though certainly they were not enjoying the fruits of the petro-dollar gusher as are their local elites.
On Day One is a social media site sponsored by the United Nations Foundation and the Better World Campaign that asks everyday people to offer their ideas about what the next president should do, figuratively "on day one." In preparation for this discussion, we solicited On Day One users for their ideas on how the next president should take on the threat of global terrorism and many people responded by suggesting that if the United States does more to alleviate poverty in the developing world the terrorist threat could be mitigated.
But is terrorism actually linked to poverty? Is it linked to other externalities, like grievances with American foreign policy, perceived humiliation, nationalist political objectives, radical ideology --- or all of the above? Which is most dominant? Which is most underestimated in current approaches to terrorism?