One of the arguments I see most frequently in support of the historical reliability of the gospels is that they were written within the lifetime of the eyewitnesses. The idea seems to be that the authors of Matthew, Mark, Luke, and John could not have gotten away with fabricating stories about Jesus because the eyewitnesses who knew the true stories would have set them straight.
The first problem with this argument is it assumes that there were eyewitnesses who knew true stories about Jesus. As I pointed out in my posts about Paul's understanding of the historical Jesus, our earliest Christian sources don't say anything about anyone having any contact with Jesus before he began making appearances after his resurrection. If the earliest Christians weren't witnesses to the events described in the gospels, they wouldn't be in a position to contradict the gospel stories.
Another problem is that we do not know that the gospels' authors weren't contradicted. As I also pointed out, references to the gospel stories by other Christian writers are not found until sometime in the second century. If the dates traditionally assigned to the gospels of 60-90 A.D. are correct, it is possible that they were contradicted by the first generation Christians who knew that the movement was not founded on the person that the gospel writers were describing. It could be that the gospel stories only came to be accepted as part of the tradition after the earliest Christians had passed from the scene.
For me, however, the biggest problem with this theory is that fanatics tend to be impervious to facts. In our present day, we have people who deny the holocaust. We have people who deny that man landed on the moon. We have people who believe that Barack Obama was born in Kenya. We have people who believe that a controlled demolition engineered by the Bush administration brought down the Twin Towers. We have people who believe that the U.S. government created the AIDS virus in order to kill Black people. We have people who believe that Jewish scientists created the AIDS virus to kill Black people. I could go on and on. There is more than enough evidence available at the click of a mouse to render all of these beliefs absurd. Nevertheless, people believe these theories with a passion that is frightening. What possible reason could we have for thinking that the earliest Christians would have been deterred by an eyewitness who asserted that the tomb was not empty?