Which is perfectly understandable; most conspiracy theories, indeed the vast majority of them are both nutty and crazy. At the very least they're ill-thought out and sorely lacking in evidentiary appeal, and at the very worst you can't get ten words into them without hearing the words "alien", "Freemason" or "Jew".
The problem is, there are sometimes conspiracies. People in the government often, well, CONSPIRE. And they conspire to do things that are often very bad. And worst of all, they conspire to cover up the evidence that they did those bad things. The problem is, there's a continuum of conspiracy theories: you start at one end with the utterly nutty (the Protocols of the Elders of Zion, or David Icke's giant space lizard theorum), proceed to the seemingly sensible but nonetheless horseshit (the innumerable JFK assassination plots, the notion that Paul Wellstone was assassinated) to the stuff that actually turned out to be a conspiracy (the Enron scandal, for example, or the Tuskeegee experiments). And since there's no middle ground, they all get lumped into the "nutty conspiracy theory" category.
And this leads to a sort of shortening of patience, so that if the theory turns out to be correct, it's as if conspiracy fatigue sets in, and no one really cares anymore. A perfect example of this would be the "Star Wars" program: Reagan's people initiated it. For years, critics claimed that it was completely unworkable -- misguided, overpriced, unwise, and scientifically unfeasible, if not outright impossible; they noted that it would also hugely enrich the defense industry, which was (and is) one of the GOP's key demographic. The Reagan team stuck to their wildly successful game plan of lie, deny, ignore, and it worked. Eventually people stopped caring about all the voices crying boondoggle. By the time the '90s rolled around, and it turned out that the critics were right -- key SDI tests were faked; the system was and always had been unworkable, and its creators knew it; and the defense contractors got fat off technology they knew was junk -- no one cared anymore. There was no outcry at all, no demand for accountability. And now, President Bush is calling for a new commitment to SDI, just as if the old one wasn't a bunch of crap.
Is this all just leading up to a lame link? It sure is. Behold, for what they are worth:
Top 10 September 11th Conspiracy Theories.