Now that Henry Kissinger has resigned as co-chair of the "independent" investigation into the 9/11 terrorist attacks, it appears that some other elder statesman with a gravelly voice will have to be found to deliver the stunning news: that pretty much everyone in the country was unprepared for what happened, and that the very few people who suspected something along those lines might be in the offing were, in retrospect, much, much more right than anyone realized at the time. (Eugene and Sasha Volokh's father suggests Tom Clancy as chair, but I expect the latter is more adept at writing spectacular fiction than pedestrian truth.)
Independent commissions of inquiry have many purposes, a few of them even legitimate. Probably their most respectable role is to act as official codifier and publicizer of some already-well-established set of facts being challenged by conspiracy theorists or generic wackos. (The Warren Commission was the prototype; it may not have been as successful as it had hoped to be, but think how wild and, uh, imaginative the Kennedy assassination conspiracy industry could have been without its careful establishment of a basic set of facts and evidence on the event.)
Finger-pointing commissions, on the other hand, are much less effective; it's much easier to believe that an august panel of dignitaries has misplaced the blame for some fiasco than that they've deliberately fabricated or covered up hard evidence. If it's politically or emotionally expedient for some people to reject the 9/11 commission's conclusion that it was, say, all Larry King's fault for failing to book Steven Emerson often enough, then they will.
Besides, how on earth can "blame" for failure to anticipate 9/11 possibly be calculated? When an event is unanticipated, that means that most people have adopted a worldview that rates such an event as highly unlikely. Now that the event has happened, of course, it's possible that their calculation of the likelihood of such a threat was grossly--even negligently--mistaken. It's also possible, though, that their calculation was completely correct. For all we know, the September 11th attack was a wildly improbable "success" that depended on numerous strokes of unbelievable luck on the terrorists' part (say, multiple near-compromises of the plot that somehow were just barely avoided). It's also possible, for all we know, that an attack viewed at the time as far more likely (say, a missile launch by a "rogue state") happened to have been derailed around the same time by some remarkable fluke of good fortune.
Indeed, even if an al Qaida attack was the most likely threat at the time, it's still possible that no reasonable information collection and analysis strategy (that is, one that did not recognize a priori the nature of the al Qaida threat) would have identified it as such. As Slate's William Saletan pointed out a few months ago, a "pattern" of evidence comparable to the one since observed regarding the September 11th attack could also have been constructed to support a prediction of any number of other disasters that, as it turned out, never came to pass. Expecting the unexpected is a very difficult business; there's just so much out there not to expect.
That doesn't mean that the government shouldn't be hard at work seeking out, studying, investigating and evaluating threats to the country, of course. What it does mean, however, is that a thorough examination of the process that missed the last threat is not likely to be particularly fruitful. (It could, for instance, spawn a "terrorist threats first" approach that will miss the next, non-terrorist danger.) A more productive exercise would be a simple best-effort threat assessment, based on the best information currently available, then an enumeration of possible countermeasures, and identification of the most cost-effective of these (in terms of estimated threat reduction potential) for implementation. I see no reason to think an "independent commission of inquiry" headed by Henry Kissinger or any other grandiose luminary would be nearly as effective as, say, a Pentagon "skunkworks" team (or perhaps several, working independently) at performing this function.