Doublas Rushkoff has just posted a thoughtful essay called "Conspiracy of Dunces" about what he sees as the problems with 9-11 conspiracies and their proponents. He's obviously attracked some heat for his opinions but I think his point that it is moving our attention away from the more important issues is right on.
9-11 theorists are unwittingly performing as the unpaid minions of the administration's propaganda wing. (At least most of them are unpaid; no doubt, some of the loudest are working as contractors for the same agencies whose activities they pretend to deconstruct.) That's why, instead of nodding along with their long-winded, preposterous yarns under the false belief that any critique is better than no critique, we--the informed, intelligent, and reasonable members of the war resistance--must instead disassociate ourselves from this drivel. In other words, we must draw the line between the kind of analysis done by Greg Palast and that done by Pilots for Truth. If we don't apply discipline to our thinking, we risk falling into the trap that even some of our best intellectuals have--like Harper's editor Lewis Lapham, who on reading a bit too much 9-11 conspiracy, has concluded that it all has some merit.
[...]
But strange and unexpected details don't necessarily point to the fallacy of the central premise--especially when the alternative involves the active coordination of thousands, if not tens of thousands of citizens in a conspiracy to attack the United States. We must look at what each intriguing detail or inconsistency actually says about how the crime took place. Again, in the words of my favorite member of the NYPD, "These explanations are principally based on the fatally flawed idea that any confusion or misinterpretation or differing accounts in times of crisis must be the product of purposeful lies. They neglect the idea that in crises, and when there is mass confusion, people do not have specific recollections, only general ones that are highly subjective, such as what direction a plane sounded like it was coming from. Their stories seek to poke holes in prevailing truth, yet offer no alternative that could be seen as remotely plausible."
A full copy is stashed in [[!the library|library/Conspiracy_of_Dunces]].
An alternative (rational) take on why the 9-11 conspriacies might be worth listening to can be found at nettime.org in the form of a book review of Peter Dale Scott's "The Road to 9/11: Wealth, Empire, and the Future of America".