People can say there are too many coincidences, but what are the odds against 4 different airplanes all being hijacked at the same time?
I don't see coincidences. I see a group of people with an axe to grind, a willingness to die, professional training, a well thought out plan, and a large bankroll, directing an attack against a largely unaware and very complacent target.
That's the problem that I have with conspiracy theories in general and this case in particular -- the available evidence, viewed without bias, supports the simplest story. We cannot prove conclusively that someone else
wasn't responsible, but my fellow forumites have not yet proven conclusively to me that the earth isn't a flat plate balanced on the back of a turtle yet, either. There is nothing wrong with questioning established wisdom in the process of refining one's personal view of life and the universe, but after a certain point the ultimate goal of such an exercise --
truth, or at least a reasonable fascimile of it -- becomes a secondary objective to the questioning itself. The entire thing becomes a philosophical exercise rather than a practical one if such questioning is pursued far enough. We can both agree that there's green grass under our feet, but are we seeing the same grass? Or the same feet?
As I said, people are free to believe what they want. My objection is when it's presented in an ignorant (or worse, intentionally deceiptful) manner to support an agenda. Most of these theories fall in this category from what I've seen.