“Those tending the pigs ran off and reported this in the town and countryside, and the people went out to see what had happened”. 
Mk 5:14 NIV 

Commercial firms know that if they advertise their product long and hard and well enough some people will buy it. But they also know that if their customers are satisfied they will tell other people and the word of a happy customer is a more powerful advert than a pamphlet in a letter-box. 
Jesus trained his disciples to become apostles and advocates of his message of eternal life through the kingdom of God. But their mission was still some way off as they accompanied him throughout Galilee whilst he taught and healed the sick. Now a dramatic healing had taken place. The demons possessing the man in the tombs had been driven out through the word of this Jesus Christ. Nothing like it had ever happened before. No doubt the pig-keepers were confused and worried. They had witnessed a miracle but lost their livelihood as their pigs went helter-skelter into the lake. So they went helter-skelter around the inhabited area to be the first to tell their families and associates about this wonder -working Jesus. And, as with the woman at the well in John’s Gospel, the people who heard the story came out to see this man for themselves. 
The role of “ordinary” Christian disciples in spreading the news about Jesus cannot be over-emphasized. Preachers and priests, pastors and teachers have a leading role to play in passing on the great message. But the disciple who can say, “I have met Jesus and he has worked a miracle in my life” makes a powerful impact and witness to anyone who will listen. 

Lord, multiply the message of those who have witnessed your grace in their lives.