Why do people believe The Da Vinci Code is real?

Over at Jesus the Radical Pastor, John Frye asks "Why do people believe the Da Vinci code?" My take on it is that Dan Brown has followed the same formula that so successfully propogates so many urban legends. That is

1. Start with an outrageous premise, but keep it just this side of impossible
2. Make sure it involves a conspiracy of some sort, meaning that people would be trying to keep it a secret
3. Provide lots of "facts," which readers could check if they wanted to, knowing full well that they in fact won't be checked

Once you combine all that with a fairly well-written book, and you've got all the makings of a cult following.