Mark 1:44 (NAB)
Then he said to him, "See that you tell no one anything, but go, show yourself to the priest and offer for your cleansing what Moses prescribed; that will be proof for them."
Mark 7:36 (NAB)
He ordered them not to tell anyone. But the more he ordered them not to, the more they proclaimed it.
Mark 8:29-30 (NAB)
And he asked them, "But who do you say that I am?" Peter said to him in reply, "You are the Messiah." Then he warned them not to tell anyone about him.
Is it just me, or does Jesus not even want anyone to know who He is? Well, at least not until the "Son of Man is lifted up". So, how much worse would it be if His disciples not only disobeyed Jesus by telling everyone the things He said to keep quiet, but also were caught with the evidence of Jesus' acts?
In any event, I think we'd have a perfectly sane and undeniably Christian Church if the Gospels were never written and only handed down through word of mouth. Of course, then we'd be playing telephone for the last 1800 years and would wind up holding on to every shred that actually was written down. The epistles were certainly necessary for creating a cohesive and orthodox Church and one would have a hard time keeping Revelation straight if it weren't written down, but I think that most everything Jesus did or said could live through word of mouth alone, as it did for probably no more than 30 years after Christ's death and resurrection.