How to find new customers

Let me tell you a quick story: A few days ago, I was visiting with a friend of mine who just recently bought a new car. (New to him, not actually brand new, as the car he just purchased is actually two years old.) One thing led to another, and during our conversation we ended up recounting the number of cars he’d bought over the last 15 years.

He was surprised to discover that he actually bought approximately 20 cars over the last 15 years.
They were almost all used cars. This did not surprise me. His answer to my next question, however, surprised both of us. The question: How many different sales people sold you all those cars? His answer: approximately 20. Not one sales person, to his knowledge, really made an ongoing effort to keep in touch with my friend. All those people who seemed so interested in him before he made a purchase seemed to vanish from the face of earth as soon as the initial purchase was completed.

Question: Is the above unusual? Are things different in your line of work?
Looking for new ways to find new customers?
My 2¢: Never forget your existing customers; never let your existing customers forget you.