Richard Carrier, in The Empty Tomb: Jesus Beyond the Grave (eds. Robert M. Price and Jeffrey Jay Lowder, Prometheus, 2005, pp. 174-176), discusses the rise of the Roswell alien spacecraft legend. He writes:
There are still people today who believe that in 1947 an alien craft crashed and was recovered, along with alien bodies, by the United States government, and that this was subsequently covered up and kept secret. Though the "core story" of a saucer crash arose immediately in 1947, the elaborations began to appear as early as 1978, when an eyewitness, Maj. Jesse Marcel, described the recovery of the spacecraft in an interview. He never recanted his story, and since then the legend has grown enormously, with numerous devoted believers. This represents a clear case of a legendary development only thirty years after the fact, with all the subsequent additions to the legend (alien bodies, government threats against witnesses, storage of the craft on a military base in Arizona, physics-defying pieces of debris, and so on) arising less than fifty years after the fact, less than twenty years after the first legendary development. Even though modern literacy, skepticism, and technology have made it possible to expose this legend with copious evidence, thousands still believe it.
Imagine if a promise of eternal life to a miserably oppressed and suffering underclass had been attached to this story, along with promises of a perfectly vicious revenge on their enemies and oppressors. Imagine that an army of the most fanatic of those who believe the story actively promoted this creed, seeing every attempt to stop them as part of the government's conspiracy, confident that their own suffering and death would be rewarded and their torturers and murderers duly punished in the end. Imagine that like many Pentecostals today, these people could "prove" their doctrine's truth by performing miraculous healings and handling of snakes, and adducing scriptures that support them. With only a little luck, could such a religion really fail to triumph?
The analogy here with the empty tomb story is strong. It turns out that the genuine historical core is that a weather balloon carrying top secret nuclear-detonation detectors (actually modified sonar buoys) fell from the sky over Roswell, was recovered by an unknowing crew involving Marcel, and really was subsequently covered up by the Air Force. Yet this historical core was obliterated within a small group of believers and entirely replaced by the legend of an alien spacecraft. If their oral tradition had just happened to be the only one to survive in print, then we would have virtually no way at all to debunk this myth--we would not even know whether it was a myth.
The only reason we know the truth in this case is because our society provides enormous resources to an investigator: huge amounts of government records accessible to anyone, a national mass media system, skeptical organizations dedicated to hunting down and publishing testimony and evidence, plus books, libraries, newspapers, universal literacy, and so on. None of this was available in antiquity. Yet even if it were we could still expect the Roswell story to flourish among many people, just as it has done today. And if such a corruption of historical tradition, the replacement of a genuine historical core with an elaborate legend, can arise in so short a time, and be believed by so many, on little more than hearsay and speculation, becoming transformed by believers into "historical fact," then certainly the same thing could have happened to the empty tomb story.
I think the Roswell legend is an excellent analogy. There was 31 years between the time of the event (1947) and the first legendary embellishment (1978). Since 1978, the legend has grown to enormous proportions. If Mark was written circa 60 CE, that would be about 30 years from the time of the death of Jesus (circa 30 CE). So if the Roswell story can be embellished in less than 30 years in modern times, why couldn't the story of Jesus be embellished in ancient times? It would have been much easier for the story to take on legendary elements in ancient times. Again to cite Carrier,
How would a myth be exploded in antiquity? They had no newspapers, telephones, photographs, or access to public documents to consult to check a story. There were no reporters, coroners, forensic scientists, or even detectives. If someone was not a witness, all people had was a man's word, and they would most likely base their judgment not on anything we would call evidence, but on the display of sincerity by the storyteller, by his ability to persuade, and impress them with a show, by the potential rewards his story had to offer, and by its "sounding right" to them. (Ibid., p. 172).
To one who is not already committed to believing (faith)in the divine inspiration of the Bible, it seems to be obvious that the Gospel account has the characteristics of a legend.