There are limits. Implicitly this means the newspapers tell people what they want to believe or are titillated by. Nobody really wants to believe the government helped in 9/11.

The "Truthers" don't have a unified narrative, however, any more than the "JFK conspiracy theorists" do. All that does them together is that they want a more complicated story, in which somebody here in the US is to blame. Perhaps people in the government, if not the WHOLE government.

In some ways these are the same types of concerns. The JFK assassination seems like quite a thing for a lone gunman to pull off, especially one with little money, a rifle almost as old as he, and a crappy manual labor job. However he had the element of surprise, plus training and complete self-confidence and lack of fear, and all that can get you a long way sometimes.

Much the same can be said of 19 Al-Qaeda agents, plus their few handlers and planners back in Egypt and Afghanistan, and their small budget. It doesn't seem possible that they did the damage they did. However, they had precisely the same advantages Oswald had.