Collier makes some observations about poor countries and then draws what seem to be ineluctable conclusions about what the richer countries should do (in this case, intervene militarily). Those who read his first book, The Bottom Billion, found his arguments very compelling. The problem was that his observations were flawed statistically, and the conclusions he drew were flawed logically, as Bill Easterly has pointed out on many occasions (including here).
There is a strong human tendency to want to do something when one sees a bad situation. It is very hard for us to just sit there and do nothing. In some sense, the history of the World Bank is a reflection of the (admirable) instinct we have to try to make bad situations better. The problem, as Easterly has pointed out, is that honorable intentions do not necessarily make for effective interventions. In fact, some interventions can make things worse, via the law of unintended consequences. The larger the intervention, the more severe the possible negative consequences.
Nonetheless, it is unlikely that the human instinct for action will go away even in the face of ferocious debunking of effectiveness by Easterly and others. So we need places where that human instinct can be channeled in ways that may be modestly effective and are unlikely to have catastrophic consequences. Nancy Birdsall, the head of the Center for Global Development, provides one of the levelest heads around on this front, by acknowledging the role that Collier has played in raising the issues and suggesting some more modest interventions that are better supported by the evidence.
Which makes me wonder why Birdsall has not yet been appointed the aid czar for the US.