Ever used that site or others like them? What is behind the gullibility of so many people? A distrust of media is, of course, one reason. But what I find interesting is that no matter how many times these myths are busted, some people will continue to forward the emails or repeat the claims. These "sources" never seem to lose their credibility.
I think a major factor is fear. A lot of people are just generally fearful of what can happen or what institutions will do, which makes them susceptible to claims.
"They" are spreading disease, grabbing guns, indoctrinating kids and on and on. In general, there is this mystery master plan that is being carried out. So be afraid. Be on guard. Believe the stories that fit the fear.