The first conspiracy theories began to emerge while the wreckage was still smouldering.
In the five years that have passed since the 9/11 attacks on the World Trade Center in New York, thousands of web pages have been devoted to the idea that the US government encouraged, permitted or actually carried out the attacks.
David Sifry (left), founder of Technorati, told Channel 4 News Radio's Morning Report: "We are tracking right now about 218 different blogs that are talking about various conspiracy theories."
"Certainly when you make it that easy for people to become creators and writers, every kook with their own theory has the ability to write his blog and get his thoughts out."
"But what we've also seen is the number of legitimate experts and people who are debunking those same theories has grown proportionally"
The Morning Report's Top of the Pods feature looks at those conspiracy theories in more detail and you can listen to them here (about 22 minutes into the show).
More memories of 9/11 on the Channel 4 News website.